CN113824086A - Setting and checking method for network-related protection fixed value - Google Patents
Setting and checking method for network-related protection fixed value Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/06—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric generators; for synchronous capacitors
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P9/00—Arrangements for controlling electric generators for the purpose of obtaining a desired output
- H02P9/006—Means for protecting the generator by using control
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P2101/00—Special adaptation of control arrangements for generators
- H02P2101/20—Special adaptation of control arrangements for generators for steam-driven turbines
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Abstract
A method for setting and checking a power grid related protection constant value aims to solve the technical problem of large power grid accidents, the power grid related protection comprises generator overspeed protection control, and the key is as follows: the rotating speed of the generator is set to be 1.02-1.03 times of the rated rotating speed, which is 3060-3090 revolutions per minute, the corresponding frequency of the generator set with the rated power lower than 300MW is set to be 50.7-51.5 Hz, and the corresponding frequency of the generator set with the rated power larger than or equal to 300MW is set to be 48.5-50.5 Hz. Through monitoring and setting the rotating speed of the generator, the currents of a rotor and a stator of the generator and the voltage value of the stator, judging and action responding of the magnetic loss condition of the generator, the magnetic loss condition of the generator and the over-excitation condition of the generator, and configuring the grid-connected protection and excitation regulators aiming at different types of generators, the power safety of the grid-connected is guaranteed in all directions, and major accidents caused by the fact that local faults cannot be protected in a larger power grid are avoided.
Description
Technical Field
The invention belongs to the technical field of power grid safety protection, relates to a method for setting and checking a power grid related protection constant value, and particularly relates to a method for setting and checking a generator parameter so as to comprehensively guarantee the power grid safety.
Background
The occurrence of many large-scale power grid accidents in China brings profound training and machine-grid coordination, namely network source coordination, to the power industry, and the consistent attention of the academic world and power production enterprises is paid. The machine-grid coordination means that a grid-connected power plant and a power grid are required to realize sufficient coordination and coordination in operation and management of primary equipment and secondary equipment, so that safe and stable operation of a power system is ensured as main content of realizing the machine-grid coordination in the aspect of relay protection, and power generator grid-related protection becomes a research hotspot. At present, the grid-related protection generally refers to a part in which action behaviors and parameter settings are related to a power grid operation mode or need to be coordinated with a safety automatic device in a power grid in generator set relay protection, and generally includes step-out protection, field-loss protection, turbine overspeed protection control, overexcitation protection, frequency abnormality protection, stator low-voltage protection, stator overvoltage protection, important auxiliary machine protection, overexcitation limitation and protection and the like of a generator set.
The existing network protection research mainly comprises the following three aspects: firstly, the research on the principle and the characteristic related to the network-related protection is carried out with the aim of improving the reliability of specific protection. According to different characteristics of the loss of field types, a new loss of field protection criterion is constructed from the aspects of reactive power, time and voltage, and a new loss of field protection scheme is designed from the perspective of coordination of a computer network; a field loss protection scheme is constructed by utilizing the synchronous potential of the generator, so that the quick action and the selectivity of field loss protection are improved; aiming at the characteristics of different types of low excitation limiters, the basic principle of setting the low excitation limit is provided from two aspects of static state and dynamic state; an improved scheme aiming at the out-of-step protection principle of the three-impedance element is provided, and the reliability of out-of-step protection and the out-of-step prediction capability are improved. The second is to study the coordination between the grid-related protection, the generator and the automatic control measure of the power grid, such as the coordination between the step-out protection and the field loss protection, the coordination between the field loss protection and the low excitation limit, and the like, and is the key point of the existing grid-related protection study; aiming at the problem of maloperation caused by overlapping of impedance characteristic areas between the step-out protection and the step-out protection, the maloperation of the step-out protection during step-out oscillation is prevented by correcting a step-out protection impedance circle, utilizing a direction locking criterion and the like; and an optimized configuration principle of overspeed protection and high-frequency generator tripping measures, a corresponding configuration scheme and the like are provided. And thirdly, research is carried out on a checking and verifying method of network-related protection. The research mainly seeks a way for rapidly realizing network-related protection and check from the perspective of engineering application. A method for checking power-related protection and related limiting measures under a large-scale power grid is provided; based on the dynamic simulation of the whole process, a corresponding method for checking the generator grid-related protection and limitation measures is provided.
In the development of modern power systems, the research on grid protection is faced with higher requirements. On the side of a power grid, application of new technologies such as extra-high voltage alternating current-direct current transmission, FACTS transmission and the like and large-scale access of new energy electric fields such as large wind power plants and the like have higher support and adjustment requirements on a large generator on the side of power generation, and the new technologies are not only used as important active power supply supporting points, and the fact that generator phase-in operation participates in voltage adjustment of the power grid becomes an important means, but when low excitation or demagnetization faults occur in the state of power generation and deep phase-in or heavy-load operation at present, impedance measured at a generator terminal is difficult to enter a reduced static stability boundary, and the situation that demagnetization protection actions are too slow or even refused can be caused, so that great threats are formed on the self safety of the generator and the stable operation on the side of the power grid, and the generator faces more severe operation conditions. On the power generation side, firstly, the capacity of a main power unit is continuously increased, the structure is more complex, the capacity of bearing abnormal operation is lower, and secondly, in a special mode operation state, the operation track of machine end measurement impedance in a real-time state cannot be mastered, so that the conditions of magnetic loss and step loss protection action are too slow or even refused, and potential safety hazards exist. Therefore, the existing research scope and technical connotation of grid-related protection have certain limitations, and the concept and technical connotation of grid-related protection must be discussed from the whole power generation side level according to the development characteristics of a power grid, and a corresponding grid-related protection construction scheme is researched.
In addition, in the aspect of research and development of a power-related protection constant value setting and checking software platform, some power plant fault analysis software systems are in existence at home at present, mainly based on in-plant equipment relay protection setting calculation, and are not subjected to data reporting and verification aiming at power-related constant values, and are also lack of matching checking of power-related protection and excitation system constant values. A mature computer-aided software system exists in the field, but the relay protection management mode of developed countries in foreign countries is different from that of China, so that the computer-aided software system is not suitable for use in China. Therefore, a software system which is in accordance with actual working conditions, powerful in function, flexible in application and has functions of related grid-related constant value management, data check and the like is needed to be developed, so that the automation level and the management level of power plant protection are improved, the management requirements of a power company on the power plant setting calculation are met, and the current digital construction requirements are met.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and designs a method for setting and checking a power grid related protection constant value.
The technical scheme adopted by the invention is that the setting and checking method of the power grid related protection constant value comprises the following steps: the rotating speed of the generator is set to be 1.02-1.03 times of the rated rotating speed, which is 3060-3090 revolutions per minute, the corresponding frequency of the generator set with the rated power lower than 300MW is set to be 50.7-51.5 Hz, and the corresponding frequency of the generator set with the rated power larger than or equal to 300MW is set to be 48.5-50.5 Hz.
The power grid related protection further comprises current overexcitation limitation and protection of a generator rotor and a generator stator, overexcitation limitation is carried out when the working current reaches 0.8-0.9 times of rated excitation current, overexcitation protection is carried out when the working current reaches 1.03-1.1 times of rated excitation current, and meanwhile, timing limit overexcitation protection is respectively set in the two working current intervals.
The power grid-related protection also comprises generator magnetic loss protection, and a composite criterion of stator impedance criterion and terminal three-phase simultaneous low voltage is adopted, wherein the stator impedance is set according to asynchronous boundary impedance circle, the action disconnection delay of a locking section with voltage is not more than 0.5 second, and the action disconnection delay of a locking section without voltage is not more than 1.0 second.
The power generator step-out protection is used for judging oscillation based on the active power of a step-out oscillation center, when the step-out oscillation center is positioned outside a power generator transformer bank, the protection action is carried out on signals, when the step-out oscillation center is positioned inside the power generator transformer bank, the step-out operation time exceeds a setting value or the current oscillation frequency exceeds a specified value, the protection action is carried out on disconnection, the number of oscillation allowed slide poles in the power generator transformer bank is not less than 2, and the number of oscillation allowed slide poles outside the power generator transformer bank is not less than 5.
The power grid-related protection also comprises stator overvoltage protection, the setting value of the stator overvoltage is determined according to the insulation condition of a stator winding, the stator overvoltage is more than or equal to 1.3 times of rated voltage, the action time limit is 0.3-0.6 s, and the protection action is in disconnection.
The power grid-related protection also comprises generator overexcitation protection, a V/Hz limiter for preventing the synchronous motor or a transformer connected with the synchronous motor from overexcitation flux is additionally arranged, and when a set of overexcitation protection is shared without a circuit breaker between the generator and the main transformer, the overexcitation multiple setting value is set to be 1.0-1.1; when a circuit breaker is arranged between the generator and the main transformer, the over-excitation multiple setting value is set to be 1.3-1.4.
The invention has the advantages that through monitoring and setting the rotating speed of the generator, the currents of the rotor and the stator of the generator and the voltage value of the stator, judging and action responding to the conditions of loss of excitation of the generator, loss of synchronism of the generator and over excitation of the generator, and configuring aiming at different types of generator grid-related protection and excitation regulators, the grid-related electric power safety is guaranteed in an all-round way, and major accidents caused by the fact that local faults cannot be protected on a larger power grid are avoided.
Drawings
Fig. 1 is an inverse time overcurrent protection trip characteristic of a rotor winding.
Fig. 2 is a logic block diagram of stator overvoltage protection.
FIG. 3 is an inverse time limit over-excitation protection action setting curve.
Fig. 4 is a low voltage ride through of auxiliary frequency converters of power plants and substations.
Fig. 5 shows a high-voltage pass-through area of auxiliary frequency converters of power plants and substations.
Detailed Description
The invention is further illustrated by the following specific examples.
A method for setting and checking a power grid related protection fixed value includes that power generator overspeed protection control is carried out, when the rotating speed of a steam turbine generator exceeds a set value or reaches a specified limiting condition, an OPC (steam turbine overspeed protection control) electromagnetic valve of a steam turbine is actuated to open, the oil pressure of a high regulating valve and a medium regulating valve is removed, and the regulating valves are closed without closing main valves.
Currently, the OPC action setpoint is typically 3090 revolutions per minute (1.03 times the nominal speed, corresponding to 51.5 Hz). The OPC resetting fixed value is reset automatically after the OPC action is set for 2s or 3s in some units; some units are reset below the set rotating speed 3060 rpm. The purpose is to make the turbine resume 3000 to operate as soon as possible, prevent the turbine overspeed. A turbo generator or a hydro generator within 300MW is required to be provided with high-frequency protection. The high-frequency protection of the turbonator is matched with a system side high-frequency generator cutting device, and the technical condition that the unit allows high-frequency operation is met. The frequency of a steam turbine with the power of 300MW or more is allowed to change within the range of 48.5-50.5 Hz during operation. The low frequency protection of the turbonator can record and indicate the accumulated frequency abnormal operation time, and each frequency is accumulated respectively.
In special cases, when the low-frequency protection needs to be tripped, the protection action time can be adjusted according to the regulations of a turbonator manufacturer, but the allowable time of each time specified in the table 1 must be met.
TABLE 1 turbo-generator frequency anomaly allowable run time
The power grid related protection further comprises current overexcitation limitation and protection of a generator rotor and a generator stator, overexcitation limitation is carried out when the working current reaches 0.8-0.9 times of rated excitation current, overexcitation protection is carried out when the working current reaches 1.03-1.1 times of rated excitation current, and meanwhile, timing limit overexcitation protection is respectively set in the two working current intervals. The generator excited by a semiconductor below 300MW can be provided with time limit over-excitation protection, and a protection belt acts on a signal in a time limit manner and reduces the excitation current.
The over-excitation protection of the 300MW and above generators can consist of two parts, namely a timing limit and a back-time limit.
The overdrive protection consists of a timing period and a back-time period.
1) And (4) timing limit overdrive protection. The timing limit overdriving protection is configured with a section of tripping and a section of signal. The action current is set according to the condition that the action current can reliably return under the rated excitation current of normal operation, namely:
in formula 1:
Krel-reliability factor, take 1.05;
IGN-primary current rating of the generator;
Krreturning the coefficient, and taking 0.9-0.95 as the condition allows to take the maximum value;
na-current transformer transformation ratio.
Rated field current I when the protection is arranged on the AC sidefdEffective value I of the converter to the ac side is 0.816I for the case of a bridge-type uncontrollable rectifierfd。
The protection delay is set according to the maximum delay of the back protection, acts on a signal, and conditionally acts on reducing the excitation current or switching excitation.
2) Inverse time limit over-excitation protection. The inverse time limit over-excitation protection consists of three parts: the method comprises the following steps of firstly, starting up a lower limit, secondly, performing an inverse time limit part, and thirdly, performing an upper limit on a fixed time limit part. The upper limit timing section sets a minimum action time constant value. The inverse time overcurrent multiple versus the corresponding allowable duration is determined by the allowable overheat condition of the rotor winding provided by the manufacturer. During setting calculation, the action characteristic of inverse time limit over-excitation protection is set to be the same as the allowable overheating characteristic of the rotor winding, as shown in fig. 1, the expression of which is:
in formula 2: c-rotor winding superheat constant;
Ifd*-forced excitation multiple.
In FIG. 1, Iop.min*Lower current per unit value, I, characteristic of inverse time-limited actionop.max*The upper limit current per unit value of the inverse time limit action characteristic is based on the rated excitation current of the generator.
The protection lower limit current fixed value is set according to the condition matched with the fixed time limit overload protection, namely:
in formula 3: kcoFor the fit coefficient, 1.05 was taken.
The upper protection limit current definite value is matched with the multiple of the forced excitation top value. If the strong excitation multiple is 2 times, when the duration time under 2 times of rated excitation current reaches the allowable duration time, the protection acts on tripping, and action delay is matched with rapid protection. When the current is less than the top value of the strong excitation and greater than the current allowed by the overload, the protection acts according to the inverse time limit characteristic.
The power grid-related protection also comprises generator magnetic loss protection, and a composite criterion of stator impedance criterion and terminal three-phase simultaneous low voltage is adopted, wherein the stator impedance is set according to asynchronous boundary impedance circle, the action disconnection delay of a locking section with voltage is not more than 0.5 second, and the action disconnection delay of a locking section without voltage is not more than 1.0 second.
Low excitation or loss of field is a common failure mode for large gensets. The damage after the demagnetization has two aspects: firstly, after the generator loses magnetism, speed difference appears between rotor and the stator magnetic field, can induce electric current in the rotor return circuit, and its frequency equals the slip frequency to arouse rotor local overheat. The generator vibrates under the impact of alternating asynchronous electromagnetic torque, and the larger the slip is, the larger the vibration is. And secondly, after the magnetic field is lost, the generator absorbs reactive power from the system, the absorbed reactive power can reach 0.9-1.2 times of the rated power of the generator, the voltage drop is large when the reactive current flows due to the large electric resistance of the transformer, the terminal voltage is seriously reduced, and the system voltage can also be seriously reduced if the reactive power of the system is insufficient.
After the loss of field, the reactive power calculation formula of the generator is as follows:
in formula 4:
Ed-generator electromotive force, kV;
Us-infinite system bus voltage value, kV;
XdΣ-total reactance from generator to infinite system;
delta-the power angle of the generator.
When there is maximum reverse reactive power, for the grid, the generator absorbing reactive power from the system threatens voltage stabilization. The large-scale generator should be equipped with a loss-of-field protection so as to find out loss-of-field faults in time and take necessary measures (such as signal sending, automatic load reduction, action on tripping and the like) so as to ensure the safety of the generator and the system.
The loss of field protection should have a multi-section scheme with different measurement principle composite criteria. The power plant closely connected with the system or the generator set adopting the self-shunt excitation mode is suitable to take the impedance criterion as one of the composite criteria of the loss-of-excitation protection, and preferentially adopts the composite criterion of the stator impedance criterion and the low voltage of the three phases at the machine end simultaneously. The system low voltage and terminal low voltage criterion of the generator field loss protection can avoid field loss protection from being refused.
The power generator step-out protection is used for judging oscillation based on the active power of a step-out oscillation center, when the step-out oscillation center is positioned outside a power generator transformer bank, the protection action is carried out on signals, when the step-out oscillation center is positioned inside the power generator transformer bank, the step-out operation time exceeds a setting value or the current oscillation frequency exceeds a specified value, the protection action is carried out on disconnection, the number of oscillation allowed slide poles in the power generator transformer bank is not less than 2, and the number of oscillation allowed slide poles outside the power generator transformer bank is not less than 5.
Different power grids have different system structures and the number of generators fed in, and dynamic events such as sudden changes in load, short-circuit fault which can not be cut off quickly enough, automatic reclosing, and change of operation mode often occur in the power grids. The occurrence of these dynamic events may cause system oscillations, which may compromise the stability of the grid. The problem of grid stability is mostly due to the oscillation of active power, which in turn will lead to slide poles (loss of mains) and unit overload.
The out-of-step protection of each generator in the same power plant is coordinated and matched on a tripping strategy, so that the simultaneous tripping of the whole plant unit caused by system disturbance is avoided. The step-out protection setting of the generator is to ensure that the generator should not be operated by mistake under the conditions of phase advance operation, short circuit fault, system oscillation, voltage loop disconnection and the like. The out-of-step protection should correctly distinguish the range in which the out-of-step oscillation center is located. The generator step-out protection is preferably operated on a signal when the oscillation center is outside the generator transformer bank, and is preferably operated on a split when the oscillation center is inside the generator transformer bank (the fixed value should match the system requirements). The number of pole slipping allowed by oscillation in the zone is not less than 2, and the number of pole slipping allowed by oscillation outside the zone is not less than 5. When the number of the units connected to the same bus system is larger than 2, the number of the oscillation slide poles in the area should be coordinated and matched, and the units in the whole plant are prevented from tripping simultaneously. The generator step-out protection should consider both preventing the generator from being damaged and reducing the damage to the system and the user caused by the step-out. To prevent the loss of mains fault from propagating to a grid accident, a certain time delay should be set for generator disconnection, so that the grid and generator have the possibility of restoring synchronization again.
The power grid-related protection also comprises stator overvoltage protection, the setting value of the stator overvoltage is determined according to the insulation condition of a stator winding, the stator overvoltage is more than or equal to 1.3 times of rated voltage, the action time limit is 0.3-0.6 s, and the protection action is in disconnection.
The setting value of the stator overvoltage protection is determined according to the allowable overvoltage capacity provided by a motor manufacturer or the insulation condition of a stator winding.
1) For steam turbine generators of 300MW and above, UopCalculated as follows:
in the formula: u shapeN-the stator nominal voltage; n isv-voltage transformer transformation ratio.
The action time is 0.5s, and the action is performed on the splitting and the demagnetization.
2) For hydro-generators, UopCalculated as follows:
the action time is 0.5s, and the action is performed on the splitting and the demagnetization.
3) For the water wheel generator excited by silicon controlled rectifier, UopCalculated as follows:
the action time is 0.3s, and the action is performed on the splitting and the demagnetization.
The logic for stator overvoltage protection is shown in fig. 2.
The power grid-related protection also comprises generator overexcitation protection, a V/Hz limiter for preventing the synchronous motor or a transformer connected with the synchronous motor from overexcitation flux is additionally arranged, and when a set of overexcitation protection is shared without a circuit breaker between the generator and the main transformer, the overexcitation multiple setting value is set to be 1.0-1.1; when a circuit breaker is arranged between the generator and the main transformer, the over-excitation multiple setting value is set to be 1.3-1.4.
V/Hz limiter, an additional element or function of a voltage regulator in the excitation system, aimed at preventing the synchronous machine or the transformer connected thereto from over-flux.
When the generator or the transformer is in over-excitation operation, the iron core generates heat, the magnetic leakage is increased, the current waveform is distorted, and the safety of the generator or the transformer is seriously damaged. For large capacity units, over-excitation protection must be provided. The over-excitation protection reflects the over-excitation multiple of the generator outlet (the low-voltage side of the transformer). When the generator and the main transformer share one set of over-excitation protection without a circuit breaker, setting values are set according to the requirement of low over-excitation capability of the generator or the transformer; when a circuit breaker is arranged between the generator and the main transformer, over-excitation protection is respectively configured for the generator and the transformer.
The parameter setting of the volt-hertz limit in the excitation regulator is matched with the characteristics of the over-excitation protection action and follows the principle that the volt-hertz limit precedes the over-excitation protection action.
Over-excitation multiple N of
In the formula:
u, f-operating voltage and frequency;
UN、fN-generator rated voltage and frequency;
U*、f*-per-value of voltage and frequency;
B、Bn-magnetic flux and nominal magnetic flux.
1) Setting two-stage fixed value and two-stage time limit for the over-excitation multiple N of the over-excitation protection at the fixed time limit.
The low fixed value part (alarm segment) is:
the high-fixed-value part (trip segment) is:
the action time limit is determined according to the overexcitation characteristics of equipment provided by a manufacturer, and generally 6.0-9.0 s can be taken. The low-fixed-value part acts on a signal in a time-limited mode and reduces the excitation current of the generator, and the high-fixed-value part acts on disconnection demagnetization or program tripping. When the over-excitation protection is configured between the generator and the transformer by a breaker, the fixed value is respectively set according to different over-excitation multiples allowed by the generator and the transformer.
2) The inverse time limit over-excitation protection is set according to an inverse time limit over-excitation characteristic curve (parameter) provided by manufacturers of generators and transformers, and has the functions of accumulation and heat dissipation. The inverse time limit over-excitation protection action setting curve is shown in figure 3. Curve 1 represents the over-excited magnetic energy curve allowed by the generator or the transformer provided by the manufacturer; and the curve 2 represents an inverse time limit overexcitation protection action setting curve.
The overexcitation inverse time-limited motion curve 2 of fig. 3 is generally not easily expressed precisely by a mathematical expression, but instead a piecewise interpolation is used to determine the relationship of n (t) and fit the curve 2. Generally, 8 to 10 points (N) are freely set on the curve 2i,ti) I is 1,2,3 …. The principle is that the points are densely arranged at the positions with large curvature. Setting the dividing point sequence requirement:
Ni＞Ni+1,ti＜ti+1or Ni＜Ni+1,ti＞ti+1(formula 11)
In the process of setting the inverse time limit overexcitation protection fixed value, a certain margin is preferably considered, and the margin can be considered from the action time and the action fixed value (one of the two is selected): when the action time is considered, the setting time can be considered to be 60-80% of the time of the curve 1; when considering from the action constant, it can be considered that the setting constant is the value of curve 1 divided by 1.05, and the minimum constant should match the timing limit low constant.
Besides the setting scheme, the net-related protection also comprises important auxiliary machine protection, including the dragging of auxiliary machine multi-purpose frequency converters such as a generator set coal feeder, a powder feeder, an air preheater, an air cooling island cooling fan and the like. The short-time (less than 5s) interruption of power supply of the frequency converter can cause equipment damage, unit shutdown or unit output power reduction to a great extent, and the safe operation of the power grid is influenced.
When the amplitude and duration of the drop of the incoming line voltage of the frequency converter caused by an external fault or disturbance are within the low-voltage crossing region, as shown in table 2, the frequency converter should be able to ensure the safe operation of the power supply object.
TABLE 2 Low-voltage ride-through region of auxiliary frequency converter of large steam turbine generator unit
| Amplitude of voltage | Rated voltage of not less than 20% | Rated voltage of not less than 60% | Rated voltage of more than or equal to 90 percent |
| Duration of low voltage | t≤0.5s | 0.5s<t≤5s | t>5s |
When the amplitude and the duration of the incoming voltage of the frequency converter caused by the frequency converter due to an external fault or disturbance are within the high voltage crossing region, as shown in table 3, the frequency converter should be able to ensure the safe operation of the power supply object.
TABLE 3 high-voltage crossover area of auxiliary frequency converter of large steam turbine generator unit
| Amplitude of voltage | Rated voltage less than or equal to 130% | Rated voltage less than or equal to 110% |
| Duration of high voltage | ≤0.5s | t>0.5s |
The low voltage crossover of the frequency converter is shown in fig. 4. When the amplitude and the duration of the voltage drop of the incoming line of the frequency converter caused by external faults or disturbances are in a low-voltage crossing area, the frequency converter should be capable of ensuring the safe operation of a power supply object.
The low voltage ride through area of the frequency converter is divided into three areas of an instantaneous low voltage ride through area, a short-time low voltage ride through area and a continuous low voltage ride through area.
The transducer is momentarily low voltage across the zone. And the amplitude of the incoming line voltage of the frequency converter is smaller than the rated voltage and is greater than or equal to 20% of the rated voltage, and the duration t is less than or equal to 0.5 s. See the area marked by the long dashed line in fig. 4.
The frequency converter passes through the area for a short time and low voltage. The amplitude of the incoming line voltage of the frequency converter is smaller than the rated voltage and is larger than or equal to 60% of the rated voltage, and the duration t is in the region of 0.5s < t ≦ 5 s. See the area marked by the short dashed line in fig. 4.
The frequency converter continues at a low voltage crossing. The amplitude of the incoming line voltage of the frequency converter is smaller than the rated voltage and is larger than or equal to 90% of the rated voltage, and the duration t is more than 5 s. See the area marked by the dotted line in fig. 4.
The high voltage ride through region of the frequency converter is shown in figure 5. When the incoming line voltage of the frequency converter caused by external faults or disturbances operates in a high-voltage crossing area, the frequency converter should be able to ensure the safe operation of the power supply object.
The high voltage ride through region of the frequency converter is divided into two regions of an instantaneous high voltage ride through region and a continuous high voltage ride through region.
The instantaneous high voltage crossing area of the frequency converter. And the amplitude of the incoming line voltage of the frequency converter is greater than the rated voltage and less than or equal to 130% of the rated voltage, and the duration t is less than or equal to 0.5 s. See the area marked by the long dashed line in fig. 5.
The frequency converter continues a high voltage crossing region. The amplitude of the incoming line voltage of the frequency converter is larger than the rated voltage and is less than or equal to 110% of the rated voltage, and the duration t is more than 0.5 s. See the area marked by the dotted line in fig. 5.
In a word, by analyzing the configuration principles of the grid-related protection and the excitation regulator of different types of generators with different capacities, the invention expounds the basic principle and the logic block diagram of the device protection aiming at each grid-related protection, and summarizes and analyzes the detailed setting method according to different principles.
Claims (6)
1. A method for setting and checking a power grid-related protection constant value is disclosed, wherein the power grid-related protection comprises generator overspeed protection control, and the method is characterized in that: the rotating speed of the generator is set to be 1.02-1.03 times of the rated rotating speed, which is 3060-3090 revolutions per minute, the corresponding frequency of the generator set with the rated power lower than 300MW is set to be 50.7-51.5 Hz, and the corresponding frequency of the generator set with the rated power larger than or equal to 300MW is set to be 48.5-50.5 Hz.
2. The method for setting and checking the grid-related protection constant value according to claim 1, characterized in that: the power grid related protection further comprises current overexcitation limitation and protection of a generator rotor and a generator stator, overexcitation limitation is carried out when the working current reaches 0.8-0.9 times of rated excitation current, overexcitation protection is carried out when the working current reaches 1.03-1.1 times of rated excitation current, and meanwhile, timing limit overexcitation protection is respectively set in the two working current intervals.
3. The method for setting and checking the grid-related protection constant value according to claim 1, characterized in that: the power grid-related protection also comprises generator magnetic loss protection, and a composite criterion of stator impedance criterion and terminal three-phase simultaneous low voltage is adopted, wherein the stator impedance is set according to asynchronous boundary impedance circle, the action disconnection delay of a locking section with voltage is not more than 0.5 second, and the action disconnection delay of a locking section without voltage is not more than 1.0 second.
4. The method for setting and checking the grid-related protection constant value according to claim 1, characterized in that: the power generator step-out protection is used for judging oscillation based on the active power of a step-out oscillation center, when the step-out oscillation center is positioned outside a power generator transformer bank, the protection action is carried out on signals, when the step-out oscillation center is positioned inside the power generator transformer bank, the step-out operation time exceeds a setting value or the current oscillation frequency exceeds a specified value, the protection action is carried out on disconnection, the number of oscillation allowed slide poles in the power generator transformer bank is not less than 2, and the number of oscillation allowed slide poles outside the power generator transformer bank is not less than 5.
5. The method for setting and checking the grid-related protection constant value according to claim 1, characterized in that: the power grid-related protection also comprises stator overvoltage protection, the setting value of the stator overvoltage is determined according to the insulation condition of a stator winding, the stator overvoltage is more than or equal to 1.3 times of rated voltage, the action time limit is 0.3-0.6 s, and the protection action is in disconnection.
6. The method for setting and checking the grid-related protection constant value according to claim 1, characterized in that: the power grid-related protection also comprises generator overexcitation protection, a V/Hz limiter for preventing the synchronous motor or a transformer connected with the synchronous motor from overexcitation flux is additionally arranged, and when a set of overexcitation protection is shared without a circuit breaker between the generator and the main transformer, the overexcitation multiple setting value is set to be 1.0-1.1; when a circuit breaker is arranged between the generator and the main transformer, the over-excitation multiple setting value is set to be 1.3-1.4.
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