GB2537705A

GB2537705A - Method and system for supplying power to primary loop of nuclear power plant during hydrostatic test

Info

Publication number: GB2537705A
Application number: GB1522287.0A
Authority: GB
Inventors: Zhou Chuangbin; Yu Weiming; Zhang Hao; Chen Jun; Zhang Zaisheng; Yang Hongxing
Original assignee: China General Nuclear Power Corp; China Nuclear Power Engineering Co Ltd
Current assignee: China General Nuclear Power Corp; China Nuclear Power Engineering Co Ltd
Priority date: 2015-04-22
Filing date: 2015-12-17
Publication date: 2016-10-26
Anticipated expiration: 2035-12-17
Also published as: GB201522287D0; CN106160202A; GB2537705B; CN106160202B

Abstract

A method and system for supplying power to a primary loop of a nuclear power plant during hydrostatic test are provided. The method comprises, a first step S1 of successively powering and starting a main pump on at least one incoming line using an auxiliary power supply and further carrying out a load limiting on the same incoming line as the main pump. A second step S2 of powering and starting a charging pump on the at least one incoming line by the auxiliary power supply. A third Step S3 of powering and starting a hydrostatic test pump by the auxiliary power supply to pressurize the primary loop to a target pressure. Finally, a fourth step S4 of automatically starting an emergency power supply on one of the at least one incoming lines to power a load if the auxiliary power supply fails in any of the above powering steps. By applying the present method no main power supply is needed to be available, and high safety and reliability are ensured.

Description

METHOD AND SYSTEM FOR SUPPLYING POWER TO PRIMARY LOOP OF NUCLEAR POWER PLANT DURING HYDROSTATIC TEST

THECHNICAL FIELD

The present invention relates to the field of commissioning of a nuclear power plant, and more particularly to a method and a system for supplying power to a primary loop of a nuclear power plant during hydrostatic test.

BACKGROUND OF THE APPLICATION

A pressurized water reactor nuclear power plant mainly comprises a pressurized water reactor, a primary loop system and a second loop system. A nuclear fission happens in a reactor core made of nuclear fuel in a pressure vessel. The low-enrichment uranium is used as the fuel of the pressurized water reactor and the light water is used as a coolant and a moderato. The heat released from the nuclear fission is carried out of the pressurized water reactor by the high pressure water flowing through the primary loop system and is transmitted to the water of the second loop in a steam generator.

After the water being heated, a steam turbine is pushed forward by the steam generated by the water. A generator is driven by the steam turbine to generate electricity.

To prevent leakage of radioactive substances, three barriers have been set between the radioactive substances (fission products) and environment. As long as one barrier is sound, the leakage of radioactive substances will not occur. A pressure boundary of the primary loop formed by the pressure vessel and pipelines connected to the pressure vessel forms the second barrier for the nuclear power plant to prevent the accidental leakage of radioactive substances. To ensure the second barrier to be sound, a hydrostatic test must be done to the pressure boundary of the primary loop before loading fuel, which is the hydrostatic test of the primary loop. When testing, the primary loop should be pressurized to a target pressure (for example, when conducting the initial hydrostatic test of the primary loop, the target pressure should be 1.25 times of the design pressure of the primary loop, and when conducting periodic tests, it should be 1.2 times of the design pressure of the primary loop) to verify if the pressure bearing capacity of the pressure vessel of the primary loop and pipelines connected to the pressure vessel meets design requirement.

The hydrostatic test of the primary loop is an oversize, high-risk, high difficult commission project of the pressurized water reactor nuclear power plant. To meet work requirements such as conducting the hydrostatic test of the primary loop, starting key equipment, jointly commissioning equipment etc., it is stipulated that when the nuclear power plant conducts the initial hydrostatic test of the primary loop, two power supplies are available to ensure an emergency start of a charging pump, that is a main power I() supply and an auxiliary power supply are available or the main power supply and an emergency diesel are available; it is also stipulated that when conducting periodic tests, three power supplies are available, that is the main power supply, the auxiliary power supply and the emergency diesel are all available.

The prior art requires the main power supply to be available when the nuclear power plant is conducted the first hydrostatic test of the primary loop and periodic tests.

However, constructions of the main power supply are often limited by external conditions involving land expropriation, removal etc., which increases work difficulty and makes the main power supply unavailable before the hydrostatic test of the primary loop. The hydrostatic test of the primary loop cannot be conducted, thus effecting the commission of the nuclear power plant.

SUMMARY OF THE APPLICATION

Aiming at above defects in the prior art, the technical problem of the present application to be solved is to provide a method and a system for supplying power to a primary loop during hydrostatic test.

In one aspect, the present application discloses a method for supplying power to a primary loop in a nuclear power plant during hydrostatic test. The method for supplying power comprises: step 1: successively powering and starting one main pump through at least one incoming line connecting to the auxiliary power supply, and limiting loads connecting to the same incoming line for the main pump start up; step 2: powering and starting one charging pump through at least one incoming line connecting to the auxiliary power supply; step 3: powering and starting the hydrostatic test pump by the auxiliary power supply to pressurize the primary loop to a target pressure; step 4: In case the auxiliary power supply lost, automatically starting an emergency power supply on the incoming line to power the loads.

Preferably, the auxiliary power supply comprises a first incoming line, a second incoming line, and a third incoming line, which are respectively used for powering three successively running main pumps configured to heat the primary loop and circulate a fluid of the primary loop; a first main pump is arranged on the first incoming line of the auxiliary power supply, a second main pump is arranged on the second incoming line of the auxiliary power supply, and a third main pump is arranged on the third incoming line of the auxiliary power supply; the charging pump comprises a first charging pump connected to an emergency AC power panel on the third incoming line and a second charging pump connected to an emergency AC power panel on the second incoming line; the two charging pumps are used to fill water to the primary loop and inject water to a shaft seal of the main pump when the hydrostatic test of the primary loop begins and used to pressurize the primary loop and balance a pressure of the primary loop through charging and discharging during the hydrostatic test of the primary loop; and the hydrostatic test pump is connected to the second incoming line.

Preferably, in step 4, the load comprises one of the following: the hydrostatic test pump, the charging pump, a component cooling water system, an essential service water system, a residual heat removal system, an uninterruptible power supply and a DC power supply.

Preferably, the method further comprises: monitoring a temperature of a tube sheet of each steam generator of the primary loop to make sure if the temperature of the whole primary loop is uniform when the main pump is running.

Preferably, the step 4 further comprises: setting a flow threshold for a discharge flow of the primary loop to limit the discharge flow of the primary loop after the auxiliary power supply fails.

Preferably, the auxiliary power supply further comprises a fourth incoming line; the first incoming line is connected to a first nuclear island unit power panel(LGM) through a first permanent plant power panel (LGB) to power the first main pump; the second incoming line is connected to a second nuclear island unit power panel(LGN) through a second permanent plant power panel (LGC) to power the second main pump; the third incoming line is connected to a third nuclear island unit power panel(LGO) through a third permanent plant power panel (LGF) to power the third main pump; and the fourth incoming line is connected to a fourth power panel to power permanent loads and public auxiliary equipment.

Preferably, the emergency AC power panel comprises a first emergency AC power panel (LHA) arranged on the first incoming line and configured to load a first nuclear island emergency load, a second emergency AC power panel (LHB) arranged on the second incoming line and configured to load a second nuclear island emergency load, and a third emergency AC power panel (LHC) arranged on the third incoming line and configured to load a third nuclear island emergency load; and each emergency AC power panel is provided with a diesel generator as emergency power supply.

Preferably, the method further comprises: detecting an outlet pressure of the charging pump or the hydrostatic test pump and closing a discharging isolation valve and a charging isolation valve if the outlet pressure is consistently under a threshold during a predetermined time.

Preferably, the method further comprises: further closing a shaft seal controlling valve.

Preferably, the method further comprises: further detecting output voltages of the second emergency AC power panel (LHB) and the third emergency AC power panel (LHC) and closing the charging isolation valve if the output voltage of the second emergency AC power panel (LHB) or of the third emergency AC power panel (LHC) is low and the outlet pressure is consistently under the threshold during the predetermined time.

Preferably, the method further comprises: further detecting output voltages of the second emergency AC power panel (LHB) and the third emergency AC power panel (LHC) and closing the charging isolation valve and the shaft seal controlling valve if the output voltage of the second emergency AC power panel (LHB) or of the third emergency AC power panel (LHC) is low and the outlet pressure is consistently under the threshold during the predetermined time.

Preferably, a second diesel generator arranged on the second incoming line has a highest availability priority in three diesel generators.

Preferably, when the second diesel generator is unavailable and a third diesel generator arranged on the third incoming line is available, using a power supply of a third 1() emergency boron pump on the second incoming line to temporarily power the hydrostatic test pump on the second incoming line.

Preferably, when the second diesel generator is unavailable and a third diesel generator arranged on the third incoming line is available, connecting a temporary power supply to a power panel of the hydrostatic test on the second incoming line to power the hydrostatic test pump on the second incoming line; the temporary power supply comes from the emergency power supply of the second incoming line.

Preferably, when the second diesel generator is unavailable and a third diesel generator arranged on the third incoming line is available, connecting a temporary power supply to a power panel of the hydrostatic test on the second incoming line to power the hydrostatic test pump on the second incoming line; the temporary power supply comes from a diesel generator with a voltage of 380V.

Preferably, when periodically re-conducting the hydrostatic test of the primary loop, both a second diesel generator and a third diesel generator are available, and thus no temporary power supply is needed.

Preferably, setting a second emergency boron pump on the second incoming line as the hydrostatic test pump.

Preferably, the method further comprises: detecting currents and temperatures of each cable between auxiliary transformers and corresponding power panels to determine if the currents and temperatures exceeds a preset value.

correspondingly, a system for supplying power to a primary loop in a nuclear power plant during hydrostatic test is provided, the system comprises: an auxiliary power supply powering a load through at least one incoming line, at least one emergency power supply, at least one main pump configured to heat the primary loop and circulate a fluid of the primary loop, at least one hydrostatic test pump and at least one charging pump; all the emergency power supply, main pump, hydrostatic test pump and charging pump are electronically connected to one incoming line, wherein, a following method for supplying power is performed by the system: step 1, successively powering and starting the main pump through at least one incoming line by the auxiliary power supply, and carrying out a load limit to a load on the 10 same incoming line as the main pump; step 2, powering and starting the charging pump on the at least one incoming line through the at least one incoming line by the auxiliary power supply; step 3, powering and starting the hydrostatic test pump by the auxiliary power supply to pressurize the primary loop to a target pressure; and step 4, automatically starting an emergency power supply on one of the at least one incoming line to power a load on the incoming line if the auxiliary power supply fails in the above powering steps.

Preferably, the emergency AC power panel comprises a first emergency AC power panel (LHA) arranged on the first incoming line and configured to load a first nuclear island emergency load, a second emergency AC power panel (LHB) arranged on the second incoming line and configured to load a second nuclear island emergency load, 25 and a third emergency AC power panel (LHC) arranged on the third incoming line and configured to load a third nuclear island emergency load; and each emergency AC power panel is configured with a diesel generator as emergency power supply. Preferably, the method further comprises: detecting an outlet pressure of the charging pump or the hydrostatic test pump and closing a discharging isolation valve and a charging isolation valve if the outlet pressure is consistently under a threshold during a predetermined time.

1() Preferably, the method further comprises: further detecting output voltages of the second emergency AC power panel (LHB) and the third emergency AC power panel (LHC) and closing the charging isolation valve and the shaft seal controlling valve if the output voltage of the second emergency AC power panel (LHB) or of the third emergency AC power panel (LHC) is low and the outlet pressure is consistently under the threshold during the predetermined time.

Preferably, when the second diesel generator is unavailable and a third diesel generator arranged on the second incoming line is available, using a power supply of a third emergency boron pump on the third incoming line to temporarily power the hydrostatic test pump on the second incoming line.

Preferably, when the second diesel generator is unavailable and a third diesel generator arranged on the second incoming line is available, connecting a temporary power supply to a power panel of the hydrostatic test on the second incoming line to power the hydrostatic test pump on the second incoming line, wherein the temporary power supply comes from the emergency power supply of the second incoming line. Preferably, when the second diesel generator is unavailable and a third diesel generator is available, connecting a temporary power supply to a power panel of the hydrostatic test on the second incoming line to power the hydrostatic test pump on the 30 second incoming line; the temporary power supply comes from a diesel generator with a voltage of 380V.

Preferably, the method further comprises: detecting currents and temperatures of each cable between auxiliary transformers and corresponding power panels to determine if the currents and temperatures exceed a preset value.

By implementing the present invention, the following advantages can be obtained.

when the main power supply is unavailable, the hydrostatic test to the primary loop can still be carried on, which makes the first hydrostatic test and periodical tests to the primary loop not limited by the main power supply during the commission of the nuclear power plant. Meanwhile the present invention provides a series of security measures for the emergency start of the charging pump after the auxiliary power supply fails and for preventing the pressure of the primary loop from greatly reducing after the diesel generator failing to start, and thus the security and reliability has been improved.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to clearly illustrate technical solution of the embodiments in accordance with the present invention or the prior art, the drawings used to describe the embodiments or the prior art will be briefly illustrated in the following. Obviously, the drawings described below are only accordance with some embodiments of the present invention. It is obvious to one of ordinary skill in the art the other drawings may be obtained without paying creative work according to these drawings.

Fig. 1 illustrates a schematic diagram of a hydrostatic test to a primary loop in accordance with the present application; Fig. 2 illustrates a flow chart of a method for supplying power in accordance with the present application; Fig. 3 illustrates a block diagram of a system for supplying power in accordance with the present application; Fig. 4 illustrates a preferred circuit of the system for supplying power shown in Fig. Fig. 5 illustrates a preferred load started and powered by an emergency power supply shown in Fig. 3; Fig. 6 illustrates a circuit diagram of a fourth power panel shown in Fig. 4; Fig. 7A illustrates a schematic diagram of power supply of a hydrostatic test pump in accordance with a first embodiment of the present application; Fig. 7B illustrates a schematic diagram of power supply of a hydrostatic test pump in accordance with a second embodiment of the present application; Fig. 7C illustrates a schematic diagram of power supply of a hydrostatic test pump in accordance with a third embodiment of the present application; Fig. 8A illustrates a schematic diagram of a method for supplying power when a diesel generator fails to start in accordance with an embodiment of the present application; Fig. 8B illustrates a schematic diagram of a method for supplying power when a diesel generator fails to start in accordance with another embodiment of the present application;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The technical solutions of the embodiments in accordance with the present invention will be clearly and completely described with reference to the drawings of the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, rather than all the embodiments. Based on these embodiments, other embodiments obtained by one of ordinary skill in the art without paying creative work fail into the protection scope of the present invention.

Fig. 1 illustrates a schematic diagram of a hydrostatic test to a primary loop. In the primary loop 100 shown in Fig. 1, a main pump 11, a steam generator 12, a pressurizer 13, a pressure vessel 14 are connected through a pipeline 10, and a volume control tank 15, a charging pump 16, a hydrostatic test pump 17, a discharging isolation valve 181, a high pressure reducer valve 182, a charging controlling valve 183, a shaft seal controlling valve 184 and a charging isolation valve 185 are used to conduct the hydrostatic test to the primary loop. During the commission of a nuclear power plant, in order to ensure the completeness of a pressure boundary of the primary loop, a hydrostatic test must be conducted to the pressure boundary of the primary loop before loading fuel, which is the hydrostatic test to the primary loop. When the hydrostatic test is conducted, the pressure of the primary loop should be set to a target pressure (for example, 1.25 times the design pressure of the primary loop) to verify if the pressure bearing capacity of the pressure vessel of the primary loop 100 and pipelines connected to the pressure vessel meets design requirements.

As shown in Fig. 1, when the hydrostatic test to the primary loop is conducted, firstly, the charging pump 16 injects water to the primary loop by charging and sealing water to the main pump to increase the pressure of the primary loop, and discharges the water out of the primary loop by discharging to reduce the pressure of the primary loop, and thus the pressure of the primary loop is increased to an outlet pressure of the charging pump 16, about 170 bar. The charging means that the water in the volume control tank 15 passes through the charging controlling valve 183 and the charging isolation valve 185 under the action of the charging pump 16 and is injected into the primary loop 100. Wherein, the charging controlling valve 183 is used to regulate a charge flow and the charging isolation valve 185 is used to open/close a charging channel. Sealing water to the main pump means that the water in the volume control tank 15 is injected into a shaft seal 111 in the main pump 11 through the shaft seal controlling valve 184 under the action of the charging pump 16 (the hydrostatic test pump 17 in the next step). The discharging means that the water in the primary loop 100 passes through the discharging isolation valve 181 and the high pressure reducer valve 182 and is injected into the volume control tank 15. Wherein, the discharging isolation valve 181 is used to open/close a discharging channel and the high pressure reducer valve 182 is used to regulate a discharge flow Then, the charging isolation valve 185 is closed and the hydrostatic test pump 17 is started. The water in the volume control tank 15 is injected into the primary loop 100 by sealing the water into main pump to increase the pressure of the primary loop, and meanwhile a discharge flow is regulated by discharging the high pressure reducer valve 182 to increase the pressure of the primary loop to a target pressure.

Fig. 1 shows two discharging channels and one charging channel. In other preferred embodiments, the number of the discharging channel and the charging channel can be regulated based on actual needs. The number of the discharging isolation valve 171, the high pressure reducer valve 182, the charging controlling valve 183, the shaft seal controlling valve 184 and the charging isolation valve 185 can also be regulated based on actual needs.

The hydrostatic test to the primary loop is an oversize, high-risk, high difficult commission project of the pressurized water reactor nuclear power plant. To meet work requirements such as conducting the hydrostatic test of the primary loop, starting key equipment, jointly commissioning equipment etc., it is stipulated that when the nuclear power plant conducts the first hydrostatic test to the primary loop, two power supplies are available to ensure an emergency start of a charging pump, namely a main power supply and an auxiliary power supply are available or the main power supply and an emergency diesel are available; it is also stipulated that when conducting periodic tests, three power supplies are available, namely the main power supply, the auxiliary power supply and the emergency diesel are all available. The problem to be solved is that what will be done if the main power supply is not used and the auxiliary power supply and the emergency diesel are used during the hydrostatic test to the primary loop, and that what measurements can be taken to make the safety performance be accepted.

The safe start of the main pump, the charging pump and the hydrostatic test pump Referring to Figs. 1-6, in the present application, when the hydrostatic test to the primary loop is conducted, the method for supplying power to the primary loop in a nuclear power plant during hydrostatic test shown in Fig. 2 is going to be performed by the system for supplying power shown in Figs. 3 and 4. As shown in Fig. 2, the method begins at step Si, that is successively powering and starting a main pump on at least one incoming line through the at least one incoming line by an auxiliary power supply, and carrying out a load limit to a load on the same incoming line as the main pump to meet capacity requirements of an auxiliary transformer on the incoming line and current requirements between the auxiliary transformer on the incoming line and a cable of a corresponding power panel.

As shown in Fig. 3, the system for supplying power comprises three incoming lines (line A, line B, line C), an auxiliary power supply 21, an auxiliary transformer 22 and an emergency power supply 23 to provide power to a load 24. As shown in Fig. 3, in the system for supplying power, a first incoming line (line A) is connected to a main pump 241, a second incoming line (line B) is connected to the main pump 241, a charging 1() pump 242, a hydrostatic test pump 243 and an emergency power supply 23, and a third incoming line (line C) is connected to the main pump 241, the charging pump 242 and the emergency power supply 23. It should be understood that in the present application the number of the incoming line of the auxiliary power supply 21 and the number of the emergency power supply 23, the main pump 241, the charging pump 242 and the hydrostatic test pump 243 can be selected. Similarly, the emergency power supply 23, the main pump 241, the charging pump 242 and the hydrostatic test pump 243 can be connected to any of the incoming line based on practical needs.

Fig. 4 shows a preferred scheme of the system for supplying power shown in Fig. 3. As shown in Fig. 4, in the preferred system for supplying power, a first main pump is arranged on the first incoming line (line A) of the auxiliary power supply, a second main pump is arranged on the second incoming line (line B) of the auxiliary power supply, and a third main pump is arranged on the third incoming line (line C) of the auxiliary power supply. Therefore, to meet capacity requirements of the auxiliary transformer and current requirements between the auxiliary transformer and a cable of a corresponding power panel, when the first main pump is started, unneeded loads on the first incoming line (line A) are prohibited to be put into operation; when the second main pump is started, unneeded loads on the second incoming line (line B) are prohibited to be put into operation; when the third main pump is started, unneeded loads on the third incoming line (line C) are prohibited to be put into operation. That is to say no matter which main pump is started, a load limit must be performed.

Take starting the first main pump for example, the following loads on the first incoming line (line A) are prohibited to be put into operation: a first pump of the condensate extraction pump system (CEX), a first pump of the electric main feed water pump system(APA), a first pump of the circulating water system, a first pump of the condensate water purification system (ATE), a first pump of the conventional island cooling water system(SRI), a first steam compressor and a third steam compressor of the boron recycle system(TEP), a first pump of the medium pressure safety injection system(RIS), a first pump of the auxiliary feed water system(ASG), a first pump of the containment heat export system, a first circulating pump of the extra cooling system.

Step S2 follows step S1, that is the charging pump on the at least one incoming line is powered and started through the at least one incoming line by the auxiliary power supply. Preferably, as shown in Fig. 4, the charging pump comprises a first charging pump connected to a third emergency AC power panel (LHC) on the third incoming line (line C) and a second charging pump connected to a second emergency AC power panel (LHB) on the second incoming line (line B). Specifically, in step S2, the first charging pump is powered by the third emergency AC power panel (LHC) on the third incoming line (line C) and the second charging pump is powered by the second emergency AC power panel (LHB) on the second incoming line (line B). The two charging pumps are used to fill water to the primary loop and inject water to a shaft seal of the main pump when the hydrostatic test of the primary loop begins and used to pressurize the primary loop and balance a pressure of the primary loop through charging and discharging during the hydrostatic test of the primary loop.

The method moves to step S3, wherein the hydrostatic test pump is powered and started by the auxiliary power supply to pressurize the primary loop to a target pressure.

When the first hydrostatic test of the primary loop is conducted, the target pressure is usually to be 1.25 times the design pressure of the primary loop, and when the periodic tests are conducted, it should be 1.2 times the design pressure of the primary loop. Preferably, as shown in Fig. 4, the second emergency boron pump connected to the second incoming line (line B) is also used as the hydrostatic test pump. Specifically, in step S3, the primary loop is pressurized through the hydrostatic test pump powered by the second incoming line (line B) to achieve the target pressure. The emergency boron pump is an inherent equipment of the nuclear power plant and is used to add emergency material containing boron such as boric acid to a reactor cooling system of the nuclear power plant. Using the emergency boron pump as the hydrostatic test pump, experimental costs can be saved, and test equipment and arrangements of wire can be simplified.

If the auxiliary power supply fails in the above powering steps, step S4 of the method is performed, that is the emergency power supply on one of the at least one incoming line is automatically started to power a load on the incoming line. As shown in Fig. 5, when the auxiliary power supply fails, the following loads 24 are powered and started by the emergency power supply 23: a charging pump 242, a hydrostatic test pump 243, a component cooling water system 244, an essential service water system 245, a residual heat removal system 246, an uninterruptible power supply 247 and a DC power supply 248. Wherein, the hydrostatic test pump 243 and the residual heat removal system 246 are chosen to be started. If the hydrostatic test pump 243 or the residual heat removal system 246 is in a running state before the auxiliary power supply fails, the hydrostatic test pump 243 or the residual heat removal system 246 is powered and started by the emergency power supply 23 after the auxiliary power supply fails, otherwise they are not started. The component cooling water system 244 is used to supply cooling water to equipment needed to be used when the reactor is in a normal state and in an accident condition. The essential service water system 245 is used to export heat from the component cooling water system 244 and discharge the heat to a final hot trap such as seawater. The residual heat removal system 246 is used to discharge extra heat of the reactor when the reactor is cooled down. The uninterruptible power supply 247 and the DC power supply 248 are used to power a digital control system (DCS) of the nuclear power plant.

By applying step S4, when the auxiliary power supply fails, uncontrollable safety problems caused by the losses of power of important equipment and systems of the nuclear power plant can be avoided, thus improving the safety and controllability of the method for supplying power. Preferably, as shown in Fig. 4, a second diesel generator (LHQ) and a third diesel generator (LHR) are used as emergency power supply. Of course, the skilled person in the art can chose other power supplies as emergency power supply according to the actual situation.

Preferably, to prevent the pressure of the primary loop from suddenly reducing after the auxiliary power supply fails, a flow threshold is previously set for the discharge flow of the primary loop to limit the discharge flow of the primary loop. The moment of the auxiliary power supply losing power, the bigger the discharge flow is, the faster the pressure of the primary loop reduces, and thus generating a big transient impact. As shown in Fig. 1, to reduce the transient impact, the discharge flow of the primary loop 100 can be limited by setting the flow threshold of the high pressure reducer valve 182.

By performing the method for supplying power of the embodiment, when the main power supply is unavailable, three main pumps and two charging pumps can be started by the auxiliary power supply to conduct the hydrostatic test of the primary loop, thus making the commission of the nuclear power plant unlimited by the main power supply.

In a preferred embodiment of the present application, the method performed by the system for supplying power further comprises: monitoring a temperature of a tube sheet of each steam generator of the primary loop to make sure if the temperature of the whole primary loop is uniform when the main pump is running. As shown in the system for supplying power in Fig. 4, theoretically, when a single main pump is running, loops of the other two main pumps out of action still have enough reverse flow to make fluid of the whole primary loop fully circulated, thus making the temperature uniform. When the hydrostatic test of the primary loop is actually conducted, to make sure that the temperature of the whole primary loop is uniform, the temperature of the primary loop needs to be monitored. As shown in Fig. 1, in the present application the temperature of the tube sheet 121 of the steam generator 12 of the primary loop 100 is monitored to ensure if the temperature of the whole primary loop 100 is uniform. As shown in the system for supplying power in Fig. 4, the primary loop comprises three main pumps and three corresponding steam generators. Specifically, the method of monitoring temperature at least can be that at least one temperature sensor is stuck at the outer surface of each tube sheet to measure the temperature of the tube sheet. If a temperature difference of all the tube sheets is within a prescribed limit, such as 2-5°C, the temperature of the whole primary loop is thought to be uniform. Of course, in other preferred embodiments, the method of the prior art can be employed to perform the temperature monitoring. The present embodiment fully ensures the practicability of successively running the main pump to conduct hydrostatic test of the primary loop.

In another preferred embodiment of the present application, the method performed by the system for supplying power further comprises: detecting currents and temperatures of each cable between auxiliary transformers and corresponding power panels to determine if the currents and temperatures exceed a preset value. If the 10 currents and temperatures exceed the preset value, the main pump is stopped. As shown in Fig. 4, cables comprise electric cables between the auxiliary transformer and a first power panel (LGB), a second power panel (LGC), a third power panel (LGF) and a fourth power panel.

As shown in Fig. 4, in the system for supplying power of the present embodiment, LGA, LGD and LGE are unit power panels and used to connect auxiliary equipment and some peripheral equipment needed by the unit in a normal running state. When the unit is stopped, these power panels are stopped successively.

LGM, LGN, LGO and LGP are nuclear island unit power panels and used to power large-scale electrical equipment of the nuclear island safety building the reactor building and the nuclear auxiliary building and distribute an AC power source with a low pressure of 380V. Wherein, the first main pump is powered by LGM, the second main pump is powered by LGN, and the third main pump is powered by LGO.

LGB, LGC and LGF are permanent plant power panels and used to connect important auxiliary equipment. When the unit is stopped, these power panels are needed to be in a running state to make sure that the unit can be normally started and stopped.

Three emergency AC power panels (LHA, LHB, LHC) with a middle pressure of 10kV are respectively arranged on the first incoming line (line A), the second incoming line (line B), and the third incoming line (line C) of the auxiliary power supply. The first power panel (LHA) is configured to load a first nuclear island emergency load. The 30 second power panel (LHB) is configured to load a second nuclear island emergency load.

The third power panel (LHA) is configured to load a third nuclear island emergency load. A first diesel generator (LHP), a second diesel generator (LHQ) and a third diesel generator (LHR) are respectively arranged on the first emergency AC power panel (LHA), the second emergency AC power panel (LHB) and the third emergency AC power panel (LHC) to be used as emergency power supply within the nuclear plant. In a normal state, the three emergency AC power panels are powered by the main power supply or the auxiliary power supply. In an accident state, they are powered by the diesel generators. As shown in Fig. 4, the pressure of 10kV of the first emergency AC power panel (LHA) is transformed to a pressure of 380V through a first voltage transformer and used to power a first emergency boron pump through a first power panel (LLE). Similarly, the pressure of 10kV of the second emergency AC power panel (LHB) is transformed to a pressure of 380V through a second voltage transformer and used to power a second emergency boron pump through a second power panel (LLH). The pressure of 10kV of the third emergency AC power panel (LHC) is transformed to a pressure of 380V through a third voltage transformer and used to power a third emergency boron pump through a third power panel (LLC). Preferably, the second emergency boron pump is also used as the hydrostatic test pump. Of course, the first emergency boron pump or the third emergency boron pump can also be used as the hydrostatic test pump according to the practical design needs. Another pump is also can be added to be used as the hydrostatic test.

The unit power panels, the permanent plant power panels and the emergency AC power panels are divided into three power supply series. In the prior art, when the hydrostatic test of the primary loop is conducted, these three power supply series and a fourth power panel in the nuclear plant are generally powered by a power grid of 500kV through a main switch station and a main voltage transformer, and the auxiliary power supply or the diesel generator is backup. Wherein, the fourth power panel comprises a public power panel used for powering public auxiliary equipment. However, in the present application, when the hydrostatic test of the primary loop is conducted, these three power supply series and the public power panel in the nuclear plant are powered by the auxiliary power supply through auxiliary transformers. As shown in Fig. 4, the Is auxiliary power supply comprises four independent incoming lines, wherein, the first incoming line (line A) is connected to the first nuclear island unit power panel (LGM) through the first permanent plant power panel (LGB) to power the first main pump; the second incoming line (line B) is connected to the second nuclear island unit power panel (LGN) through the second permanent plant power panel (LGC) to power the second main pump; the third incoming line (line C) is connected to the third nuclear island unit power panel (LGO) through the third permanent plant power panel (LGF) to power the third main pump; the fourth incoming line is connected to the fourth power panel to power permanent loads and public auxiliary equipment.

As shown in Fig. 6, the fourth power panel in Fig. 4 comprises a fourth permanent plant power panel (LGH) connected to the fourth incoming line of the auxiliary power supply, a fourth unit power panel (LGG) connected to the incoming line of the main power supply, a fourth nuclear island unit power panel (LGQ) connected to the fourth permanent plant power panel (LGH), a first public power panel (8LGIA) connected to the fourth permanent plant power panel (LGH) and a second public power panel (8LGIB) connected to the first public power panel (8LGIA).

Emergency start of the charging pump In the method for supplying power to the primary loop in a nuclear power plant during hydrostatic test provided by the present application, the safety start of the charging pump and the hydrostatic test pump is powered by the auxiliary power supply. If the auxiliary power supply fails, the diesel generator and the charging pump are started in emergency to make sure the main pump sealed and injected to maintain the pressure of the primary loop, thus the safety of the equipment is guaranteed.

When the auxiliary power supply fails, the diesel generator on one of the incoming lines and the charging pump, the component cooling water system, the essential service water system and the residual heat removal system on the corresponding incoming line are automatically started, and the uninterruptible power supply and the DC power supply on the corresponding incoming line are powered by the diesel generator. As shown in Fig. 4, the first charging pump is arranged on the third incoming line (line C) and the second charging pump is arranged on the second incoming line (line B). The two charging pumps are used to fill water to the primary loop when the hydrostatic test of the primary loop begins and used to pressurize the primary loop and balance a pressure of the primary loop through charging and discharging during the hydrostatic test of the primary loop. Specifically, since the charging pump is not arranged on the first incoming line (line A), the availability of the first diesel generator on the first incoming line (line A) is not required here. The second diesel generator on the second incoming line (line B) has a highest availability priority, which can power the second charging pump and the hydrostatic test pump to guarantee their emergency power supply. Wherein, the hydrostatic test pump is the second emergency boron pump in Fig. 4. When the second diesel generator on the second incoming line (line B) is unavailable and the third diesel generator is available, measurements are needed to be taken to make sure that there are two power supplies in the hydrostatic test pump to improve the reliability and safety of the power supply during the experiment.

When the pressure exceeds an outlet pressure of the charging pump, the hydrostatic test pump is used alone for pressurization. When the auxiliary power supply fails, the hydrostatic test pump is required to be started. As shown in Fig. 4, the hydrostatic test pump is powered by the second emergency power supply (that is the second diesel generator (LHQ)). When the second diesel generator (LHQ) is available, the emergency power supply of the hydrostatic test pump can be guaranteed to make sure that the hydrostatic test pump can be started when the auxiliary power supply fails.

When the third diesel generator (LHR) is available and the second diesel generator (LHQ) is unavailable, temporary measurements are applied to make sure that there are two power supplies in the hydrostatic test pump. The following three preferred schemes are used to make sure that there are two power supplies in the hydrostatic test pump.

As shown in Fig. 7A, in the first preferred scheme, the hydrostatic test pump on the second incoming line (line B) that is the second emergency boron pump is temporarily powered by the third emergency boron pump on the third incoming line (line C). The third power panel (LLC) with a voltage of 380V of the third emergency boron pump on the third incoming line (line C) is temporarily connected to the second emergency boron pump on the second incoming line (line B) to power it.

As shown in Fig. 7B, in the second preferred scheme, a temporary power supply is connected to the hydrostatic test pump on the second incoming line (line B) that is the second power panel (LLH) of the second emergency boron pump. The temporary power supply comes from an emergency power supply with a voltage of 380V on the third incoming line (line C).

As shown in Fig. 7C, in the third preferred scheme, another temporary power supply is connected to the hydrostatic test pump on the second incoming line (line B) that is the second power panel (LLH) of the second emergency boron pump. The temporary power supply comes from a temporary diesel generator with a voltage of 380V.

Thus the emergency start of the hydrostatic test pump is guaranteed.

A first hydrostatic test is needed to be conducted in the primary loop of the new-built nuclear power plant. However, the hydrostatic test of the primary loop is often re-conducted by the nuclear power plant in service every ten years. When the hydrostatic test of the primary loop is periodically re-conducted, considering the nuclear power plant in service has more risk points, both the second diesel generator (LHQ) and the third diesel generator (LHR) are required to be available when being powered by the auxiliary power supply, thus no temporary power supply is needed to be provided for the hydrostatic test pump.

The scheme of emergency start provided for the charging pump and the hydrostatic test by the present embodiment can make sure that there are always two power supplies, thus improving the reliability and safety during the hydrostatic test of the primary loop.

Measurements when the auxiliary power supply is lost and the diesel generator is unable to be started If the auxiliary power supply is lost during the hydrostatic test of the primary loop and the emergency start of the diesel generator is unsuccessful, the emergency AC power panels (LHA, LHB and LHC) will lose power, thus making the primary loop losing the pressure source provided by the charging pump or the hydrostatic test pump. By this time, if no measurement is taken, the pressure of the primary loop will lose control, and thus making serious consequences. Therefore, the method for supplying power provided by the present application provides further measurements to prevent these consequences.

The method for supplying power performed by the system provided by the present I() application further comprises: detecting an outlet pressure of the charging pump or the hydrostatic test pump and automatically closing a discharging isolation valve and a charging isolation valve if the outlet pressure is consistently under a threshold during a predetermined time and selectively automatically closing a shaft seal controlling valve. If the outlet pressure of the charging pump or the hydrostatic test is under the threshold, it means that the charging pump or the hydrostatic test pump is unsuccessfully started, that is the auxiliary power supply fails and the diesel generator is unsuccessfully started. Wherein, the connecting relations of the charging pump, the hydrostatic test pump, the discharging isolation valve, the charging isolation valve and the shaft seal controlling valve are shown as Fig. 1. That is, as shown in Fig. 8A, if the outlet pressure of the charging pump or the hydrostatic test pump is low during a predetermined time delay, the discharging isolation valve and the charging isolation valve are automatically closed, and the shaft seal controlling valve are selectively automatically closed. Of course, users also can manually close the above valves according to the outlet pressure representing the situation of the charging pump or the hydrostatic test pump.

In another preferred embodiments of the present application, the closing of the charging isolation valve and the shaft seal controlling valve further depends on the voltage value of the second emergency AC power panel (LHB) or of the third emergency AC power panel (LHC). Therefore, the charging isolation valve and the shaft seal controlling valve are prevented from being closed by mistake when the charging pump is not started at the beginning of the water injection. As shown in Fig. 8B, if the voltage of the second emergency AC power panel (LHB) or of the third emergency AC power panel (LHC) is low and the output voltage of the second emergency AC power panel (LHB) or of the third emergency AC power panel (LHC) is consistently a threshold during a predetermined time, the charging isolation valve is automatically closed and the shaft seal controlling valve is selectively automatically closed. The voltage of the second emergency AC power panel (LHB) or of the third emergency AC power panel (LHC) is low, which directly proves that the auxiliary power supply fails and the diesel is unsuccessfully started. Therefore, by detecting the voltage of the second emergency AC power panel (LHB) and the third emergency AC power panel (LHC), it can effectively be avoided that the charging isolation valve and the shaft seal controlling valve are closed by mistake.

By performing the method for supplying power and system for supplying power to the primary loop in a nuclear power plant during hydrostatic test provided by the embodiment, even if both the auxiliary power supply and the diesel generator lose power at the same time, the system for supplying power of present application can control the primary loop, thus avoiding the safety problems caused by the suddenly power failure or the suddenly power re-supply.

While the present application has been described with reference to preferred embodiments, the present application is not limited to above specific embodiments which are only illustrative, but not for the purpose of limiting. It will be understood by those skilled in the art that various changes may be made and equivalents may be substituted under the inspiration of the present application without departing from the scope of the present application. However, all the changes and equivalents will be included within the scope of the appended claims.

Claims

CLAIMS: 1. A method for supplying power to primary loop in a nuclear power plant during hydrostatic test, comprising: S1, successively powering and starting a main pump on at least one incoming line through the at least one incoming line by an auxiliary power supply, and carrying out a load limit to a load on the same incoming line as the main pump; S2, powering and starting a charging pump on the at least one incoming line through the at least one incoming line by the auxiliary power supply; S3, powering and starting a hydrostatic test pump by the auxiliary power supply to pressurize the primary loop to a target pressure; and S4, automatically starting an emergency power supply on one of the at least one incoming line to power a load on the incoming line if the auxiliary power supply fails in above powering steps.
2. The method for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 1, wherein, the auxiliary power supply comprises a first incoming line, a second incoming line, and a third incoming line, which are respectively used for powering three successively running main pumps configured to heat the primary loop and circulate a fluid of the primary loop; a first main pump is arranged on the first incoming line of the auxiliary power supply, a second main pump is arranged on the second incoming line of the auxiliary power supply, and a third main pump is arranged on the third incoming line of the auxiliary power supply; the charging pump comprises a first charging pump connected to an emergency AC power panel on the third incoming line, and a second charging pump connected to an emergency AC power panel on the second incoming line; the two charging pumps are used to fill water to the primary loop and inject water to a shaft seal of the main pump when the hydrostatic test of the primary loop begins and used to pressurize the primary loop and balance a pressure of the primary loop through charging and discharging during the hydrostatic test of the primary loop; and the hydrostatic test pump is connected to the second incoming line.
3. The method for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 1, wherein, in step S4, the load comprises one of the following: the hydrostatic test pump, the charging pump, a component cooling water system, an essential service water system, a residual heat removal system, an uninterruptible power supply and a DC power supply.
4. The method for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 1, wherein, the method further comprises: monitoring a temperature of a tube sheet of each steam generator of the primary loop to make sure if the temperature of the whole primary loop is uniform when the main pump is running.
5. The method for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 1, wherein, the step S4 further comprises: setting a flow threshold for a discharge flow of the primary loop to limit the discharge flow of the primary loop after the auxiliary power supply fails.
6. The method for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 2, wherein, the auxiliary power supply further comprises a fourth incoming line; the first incoming line is connected to a first nuclear island unit power panel (LGM) through a first permanent plant power panel (LGB) to power the first main pump; the second incoming line is connected to a second nuclear island unit power panel 20 (LGN) through a second permanent plant power panel (LGC) to power the second main pump; the third incoming line is connected to a third nuclear island unit power panel (LGO) through a third permanent plant power panel (LGF) to power the third main pump; and the fourth incoming line is connected to a fourth power panel to power permanent loads and public auxiliary equipment.
7. The method for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 2, wherein, the emergency AC power panel comprises a first emergency AC power panel (LHA) arranged on the first incoming line and configured to load a first nuclear island emergency load, a second emergency AC power panel (LHB) arranged on the second incoming line and configured to load a second nuclear island emergency load, and a third emergency AC power panel (LHC) arranged on the third incoming line and configured to load a third nuclear island emergency load; and each emergency AC power panel is provided with a diesel generator as an emergency power supply.
8. The method for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 7, wherein, the method further comprises: detecting an outlet pressure of the charging pump or the hydrostatic test pump and closing a discharging isolation valve and a charging isolation valve if the outlet pressure is consistently under a threshold during a predetermined time.
9. The method for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 8, wherein, the method further comprises: further closing a shaft seal controlling valve.
10.The method for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 8, wherein, the method further comprises: further detecting output voltages of the second emergency AC power panel (LHB) and the third emergency AC power panel (LHC) and closing the charging isolation valve if the output voltage of the second emergency AC power panel (LHB) or of the third emergency AC power panel (LHC) is low and the outlet pressure is consistently under the threshold during the predetermined time.
11.The method for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 9, wherein, further detecting output voltages of the second emergency AC power panel (LHB) and the third emergency AC power panel (LHC) and closing the charging isolation valve and the shaft seal controlling valve if the output voltage of the second emergency AC power panel (LHB) or of the third emergency AC power panel (LHC) is low and the outlet pressure is consistently under the threshold during the predetermined time.
12. The method for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 7, wherein, a second diesel generator arranged on the second incoming line has a highest availability priority among three diesel generators.
13. The method for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 12, wherein, when the second diesel generator is unavailable and a third diesel generator arranged on the third incoming line is available, using a power supply of a third emergency boron pump on the third incoming line to temporarily power the hydrostatic test pump on the second incoming line.
14. The method for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 12, wherein, when the second diesel generator is unavailable and a third diesel generator arranged on the third incoming line is available, connecting a temporary power supply to a power panel of the hydrostatic test on the second incoming line to power the hydrostatic test pump on the second incoming line; the temporary power supply comes from the emergency power supply of the second incoming line.
15. The method for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 12, wherein, when the second diesel generator is unavailable and a third diesel generator arranged on the third incoming line is available, connecting a temporary power supply to a power panel of the hydrostatic test on the second incoming line to power the hydrostatic test pump on the second incoming line; the temporary power supply comes from a diesel generator with a voltage of 380V.
16. The method for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 7, wherein, when periodically re-conducting the hydrostatic test of the primary loop, both a second diesel generator and a third diesel generator are available, and thus no temporary power supply is needed.
17. The method for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 2, wherein, setting a second emergency boron pump on the second incoming line as the hydrostatic test pump.
18. The method for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 2, wherein, the method further comprises: detecting currents and temperatures of each cable between auxiliary transformers and corresponding power panels to determine if the currents and temperatures exceed a preset value.
19. A system for supplying power to a primary loop in a nuclear power plant during hydrostatic test, wherein, the system comprises: an auxiliary power supply powering a load through at least one incoming line, at least one emergency power supply, at least one main pump configured to heat the primary loop and circulate a fluid of the primary loop, at least one hydrostatic test pump and at least one charging pump; each emergency power supply, each main pump, each hydrostatic test pump and each charging pump are respectively electronically connected to one incoming line, wherein, a following method for supplying power is performed by the system: S1, successively powering and starting the main pump on the at least one incoming line through the at least one incoming line by the auxiliary power supply, and carrying out a load limit to a load on the same incoming line as the main pump; S2, powering and starting the charging pump on the at least one incoming line through the at least one incoming line by the auxiliary power supply; S3, powering and starting the hydrostatic test pump by the auxiliary power supply to pressurize the primary loop to a target pressure; and S4, automatically starting an emergency power supply on one of the at least one incoming line to power a load on the incoming line if the auxiliary power supply fails in the above powering steps.
20. The system for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 19, wherein, the auxiliary power supply comprises a first incoming line, a second incoming line, and a third incoming line, which are respectively used for powering three successively running main pumps configured to heat the primary loop and circulate a fluid of the primary loop; a first main pump is arranged on the first incoming line of the auxiliary power supply, a second main pump is arranged on the second incoming line of the auxiliary power supply, and a third main pump is arranged on the third incoming line of the auxiliary power supply; the charging pump comprises a first charging pump connected to an emergency AC power panel on the third incoming line and a second charging pump connected to an emergency AC power panel on the second incoming line; the two charging pumps are used to fill water to the primary loop and inject water to a shaft seal of the main pump when the hydrostatic test of the primary loop begins and used to pressurize the primary loop and balance a pressure of the primary loop through charging and discharging during the hydrostatic test of the primary loop; and the hydrostatic test pump is connected to the second incoming line.
21. The system for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 19, wherein, in step S4, the load comprises one of the following: the hydrostatic test pump, the charging pump, a component cooling water system, an essential service water system, a residual heat removal system, an uninterruptible power supply and a DC power supply.
22. The system for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 19, wherein, the method further comprises: monitoring a temperature of a tube sheet of each steam generator of the primary loop to make sure if the temperature of the whole primary loop is uniform when the main pump is running.
23. The system for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 19, wherein, the step S4 further comprises: setting a flow threshold for a discharge flow of the primary loop to limit the discharge flow of the primary loop after the auxiliary power supply fails.
24. The system for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 20, wherein, he auxiliary power supply further comprises a fourth incoming line; the first incoming line is connected to a first nuclear island unit power panel (LGM) through a first permanent plant power panel (LGB) to power the first main pump; the second incoming line is connected to a second nuclear island unit power panel (LGN) through a second permanent plant power panel (LGC) to power the second main pump; the third incoming line is connected to a third nuclear island unit power panel (LGO) through a third permanent plant power panel (LGF) to power the third main pump; and the fourth incoming line is connected to a fourth power panel to power permanent loads and public auxiliary equipment.
25. The system for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 20, wherein, the emergency AC power panel comprises a first emergency AC power panel (LHA) arranged on the first incoming line and configured to load a first nuclear island emergency load, a second emergency AC power panel (LHB) arranged on the second incoming line and configured to load a second nuclear island emergency load, and a third emergency AC power panel (LHC) arranged on the third incoming line and configured to load a third nuclear island emergency load; and each emergency AC power panel is provided with a diesel generator as an emergency power supply.
26. The system for supplying power to the primary loop in a nuclear power plant 1() during hydrostatic test of claim 25, wherein, the method further comprises: detecting an outlet pressure of the charging pump or the hydrostatic test pump and closing a discharging isolation valve and a charging isolation valve if the outlet pressure is consistently under a threshold during a predetermined time.
27. The system for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 26, wherein, the method further comprises: further closing a shaft seal controlling valve.
28. The system for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 26, wherein, he power supply method further comprises: further detecting output voltages of the second emergency AC power panel (LHB) and the third emergency AC power panel (LHC) and closing the charging isolation valve if the output voltage of the second emergency AC power panel (LHB) or of the third emergency AC power panel (LHC) is low and the outlet pressure is consistently under the threshold during the predetermined time.
29. The system for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 27, wherein, the power supply method further comprises: further detecting output voltages of the second emergency AC power panel (LHB) and the third emergency AC power panel (LHC) and closing the charging isolation valve and the shaft seal controlling valve if the output voltage of the second emergency AC power panel (LHB) or of the third emergency AC power panel (LHC) is low and the outlet pressure is consistently under the threshold during the predetermined time.
30. The system for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 25, wherein, a second diesel generator arranged on the second incoming line has a highest availability priority in three diesel generators.
31. The system for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 30, wherein, when the second diesel generator is unavailable and a third diesel generator arranged on the second incoming line is available, using a power supply of a third emergency boron pump on the third incoming line to temporarily power the hydrostatic test pump on the second incoming line.
32. The system for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 30, wherein, when the second diesel generator is unavailable and a third diesel generator arranged on the second incoming line is available, connecting a temporary power supply to a power panel of the hydrostatic test on the second incoming line to power the hydrostatic test pump on the second incoming line, wherein the temporary power supply comes from the emergency power supply of the second incoming line.
33. The system for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 30, wherein, when the second diesel generator is unavailable and a third diesel generator is available, connecting a temporary power supply to a power panel of the hydrostatic test on the second incoming line to power the hydrostatic test pump on the second incoming line; the temporary power supply comes from a diesel generator with a voltage of 380V.
34. The system for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 25, wherein, when periodically re-conducting the hydrostatic test of the primary loop, both a second diesel generator and a third diesel generator are available, and thus no temporary power supply is needed.
35. The system for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 20, wherein, setting a second emergency boron pump on the second incoming line as the hydrostatic test pump.
36. The system for supplying power to the primary loop in a nuclear power plant during hydrostatic test of claim 20, wherein, the method further comprises: detecting currents and temperatures of each cable between auxiliary transformers and corresponding power panels to determine if the currents and temperatures exceed-a preset value.