JPH10112931A - High-speed current limiting breaker for gas turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To with the system accident without installing a breaker excellent in high-speed breaking performance in every generator, by outputting a trip signal, when the load current flowing in a load power supply circuit from the generator gets over a predetermined value, separately for each generator, and opening a vacuum switch prior to a vacuum breaker. SOLUTION: Power generation systems I, II to V comprises overcurrent relays (OCR-H) 18-1, 18-2 to 18-5 driven by gas turbines 1-1, 1-2 to 1-5, and vacuum breakers (VCB) 4-1, 4-2 to 4-5. When this system detects a load current through CT from the power supply circuit to load from the generator 3-1 (3-2 to 3-5) and detects overload in the (OCR-H) 18-1 (18-2, 18-5), this outputs a trip signal. A trip control circuit 200 breaks the vacuum switch (VS) 17 and VCB 12, receiving the trip signal from (OCR-H) 18-1 (18-2 to 18-5).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-speed current-limiting device for a gas turbine in an interconnection operation between a plurality of gas turbine driven generators and a commercial power supply system.

[0002]

2. Description of the Related Art Conventionally, there has been known a system in which a generator is driven by a gas turbine to generate power. FIG. 8 is a schematic diagram of such a power generation system, wherein 1 is a gas turbine, 2 is a speed reducer for reducing the rotation speed of the output shaft of the gas turbine 1, 3 is a generator driven by the gas turbine 1, 4
Is a vacuum circuit breaker (VC) connected to the output side of the generator 1.
B), 5 are shear pins attached to the output shaft of the gas turbine 1.

[0003] Since the strength rating of the output shaft of the gas turbine 1 rotating at high speed is small, for example, an accident or the like occurs on the system side that is connected to this system, and the output shaft of the gas turbine 1 has several times the rated torque. When the above excessive torque is applied, a measure is taken to protect the gas turbine 1 by releasing the output shaft from the load by breaking the shear pin 5 attached to the output shaft.

[0004] However, once the shear pin 5 is cut, it takes several hours for the recovery operation, during which time the gas turbine cannot be used, and a demand over may occur. Therefore, when a situation occurs in which an excessive torque is applied to the gas turbine, there has been a demand for a shutoff device that instantaneously detects the occurrence and shuts off the output side of the generator at high speed.

[0005]

Conventionally, a vacuum circuit breaker (VCB) has been used as a protection device for a shear pin in an interconnection operation between a plurality of power generation systems driven by gas turbines as described above and a commercial power supply system. And those using a semiconductor switch are known.

FIG. 9 shows an example of a protection device using a VCB. For example, each of five power generation systems detects an overload such as an overcurrent relay (OCR-H) or an undervoltage relay (UVR). Apparatus 6-1,..., 6
5 detects an overload applied to the gas turbines 1-1,..., 1-5, issues a trip signal, and outputs a vacuum circuit breaker (V
CB) 4-1..., 4-5 are electrically cut off. In the figure, reference numeral 10 denotes a commercial power supply system that is connected to the generator 3, 11 denotes a transformer, and 12 denotes a vacuum circuit breaker provided on the commercial power supply system side.

In such an interconnection operation, when the most severe accident occurs on the electric power side, for example, if the rated output of the generator is 5,000 kVA, the generator current increases with time as shown in FIG. The load on the shear pin of the gas turbine is proportional to this current, and the greater the load and the longer the load, the higher the possibility that the shear pin will break. However, since interruption time by VCB4 is the extent (60 ms at 50H _Z) 3 cycles, until the cut-off from the detection of the overload completed 10
About 0 ms or more is required. Therefore, even if the power supply circuit is cut off, the share pin may be cut off in time.

FIG. 11 shows an example of a conventional shut-off device using a semiconductor switch 7 having a higher response speed than the VCB 4. In the figure, the same reference numerals as those in FIG. 9 indicate the same components.

The interruption time by the semiconductor switch 7 is 20 m
s or less, which is considerably faster than the interruption by the VCB4, and can protect the shear pin even in the case of the above-mentioned accident. However, the price is extremely high, for example, a semiconductor used in a power generation facility of several MW (megawatt) class. When it comes to a switch, the price is over 20 million yen, and a more inexpensive shut-off device is desired.

The present invention has been made in view of the above points, and is an inexpensive high-speed current-limiting device for protecting a gas turbine in an interconnected operation system between a plurality of generators driven by a gas turbine and a commercial power supply system. The purpose is to provide.

[0011]

In order to achieve the above object, the present invention, in one aspect, includes a commercial power supply system for connecting a plurality of generators driven by a gas turbine to a commercial power supply system. A current limiting impedance and a vacuum circuit breaker connected in series to the load power supply circuit from, and a vacuum switch connected in parallel with the current limiting impedance,
A plurality of overload detectors for detecting a load current flowing through a load power supply circuit from the generator for each generator and outputting a trip signal when the detected load current exceeds a predetermined value; and A high-speed current limiting device for a gas turbine was constituted by a trip control circuit for opening a switch before the vacuum circuit breaker.

The trip control circuit is configured to release the vacuum switch and the vacuum circuit breaker in a predetermined order when a trip signal is output from any one of the plurality of overload detectors, or to prevent malfunction. At least two
It is conceivable that the vacuum switch and the vacuum circuit breaker are opened in a predetermined order when a trip signal is output from one of them. Furthermore, the overload detector is an overcurrent relay,
It is preferable that the overload is detected by full-wave rectification of the load current and DC approximation.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is an electric circuit showing one embodiment of a high-speed current limiting circuit according to the present invention. As an example, an interconnection operation between five power generation systems I, II... The system will be described. In the drawing, the same reference numerals as those in FIG. 9 indicate the same components.

The power generation system I includes a power generator 3-1 driven by a gas turbine 1-1, an overcurrent relay (OCR-H) 18-1 described later, and a VCB 4-1. Since the configurations of the power generation systems II to V are the same, the description will be omitted, and in order to facilitate the description, the rated outputs of the generators are all the same.

The power generation system I will now be described. The load current is detected from the power supply circuit from the generator 3-1 to the load via the CT, and the overcurrent relay (OCR-H ₁ ) 1 is detected.
If an overload is detected in 8-1, the trip signal T
S is output.

On the other hand, a current limiting impedance 15 composed of a resistor or a reactor is connected in series between the transformer 11 and the vacuum circuit breaker 12 in the power supply circuit of the commercial power supply system. In parallel, a power fuse 16 and a vacuum switch (VS) 17 for protection in the event of a short circuit in any of the generators 3-1 to 3-5 of the power generation systems I to V are connected in series.

Overcurrent relays 18-1, 18-2,...
The trip control circuit 200 that receives the trip signal TS from 18-5 and releases the VS 17 and the VCB 12 has the following configuration.

Reference numeral 20 denotes a trip coil (TC) for opening and closing the VS 17, and reference numeral 21 denotes a trip coil (TC) for opening and closing the VCB 12. The TC 20 is connected in series with the diode 22a and the thyristor 22b connected in parallel and in the opposite direction, and is connected between the DC power supplies pn. TC21
Is connected in series with the contact 23 and is connected between the DC power supplies pn.

On the other hand, a photodiode 25 is connected in series with the transistor 24, both are connected between the DC power supplies pn, an auxiliary relay 27 is connected in series with the transistor 26, and also connected between the DC power supplies pn. , 26 are connected to the output terminal of the OR circuit 28. The gate of the thyristor 22b is connected to the photodiode 25 and the optical fiber 29. OR circuit 2
Input terminals 8 are OCR-H18- of the power generation systems IV.
1, 18-2,..., 18-5. The OCR-H of each power generation system is conventionally known, and a value obtained by squaring the peak value of the input signal or digitally processing the absolute value is compared with a predetermined value. Is a format that outputs

Next, the operation of the high-speed current limiter will be described.

Assuming that a short-circuit accident occurs at t ₀ (t = 0), OCR-H18-1 to OCR-H18-1 will be about 10 ms later.
One of the 18-5 is the first to detect a short circuit to output a trip signal TS (time t _1). Transistors 24 and 26 receive this trip signal TS and become conductive, causing photodiode 25 to emit light and auxiliary relay 27 to be energized. The light emitted from the photodiode 25 is sent to the gate of the thyristor 22b via the optical fiber 29, whereby the thyristor 22b is turned on. Thyristor 22b
Is conducted, the TC (trip coil) 20 is energized, and the VS 17 is opened (time t ₂ ). V from accident occurrence
The time required for opening S17 is about 15 ms. VS
When the switch 17 is opened, the short-circuit current flowing through the VS 17 is suppressed to the rated current In by the current limiting impedance 15. Incidentally, the receiving voltage is 6.6 kV, and the generators 3-1 to 3-3.
Assuming that the rated output of −5 is 5,000 kVA, the rated current In, the short-circuit current Is, and the source impedance value Z required to suppress the load current to the rated current In or less are expressed by the following equation (1).
It is obtained by Equations 2 and 3.

[0023]

## EQU1 ## In = 5,000 KVA / 6.6 KV × √3 = 437A

[0024]

## EQU2 ## Is = 437A / 15% = 2,913A

[0025]

## EQU3 ## Z = 6.6 × 10 ³ V / 5,000 × 10 ³ V
A = 8.7Ω On the other hand, when the contact 23 is closed by being energized by the auxiliary relay 27, the TC (trip coil) 21 is energized and VCB
12 is opened (time t ₃ ). VCB1 from release of VS17
It is about 95 ms until the opening of No. 2. This completely shuts off the power supply circuit from the commercial power supply system 10 to the load. FIG. 2 shows changes in the generator current during this time. As apparent from FIG. 2, the generator current is suppressed to 1,742 A or less, which is much smaller than the short-circuit current Is, so that an overload on the gas turbine can be avoided and the shear pin can be protected.

Next, an overcurrent relay (OCR-H) used in the present invention will be described.

As the overcurrent relays OCR-H18-1 to 18-5 of the high-speed current limiting circuit breaker according to the present invention shown in FIG. 1, the load current is full-wave rectified, and DC is approximated to detect overload. 4 and the circuit configuration shown in FIG. 4 can exhibit more excellent high-speed cutoff performance.

High-speed overcurrent relay OCR-H1 shown in FIG.
8a uses two CTs and is called a 2CT system. The load current is detected from the two phases R and S of the three-phase power supply lines R, S, and T, which are power supply circuits to the load, via the CT and rectified by the full-wave rectifier circuit 30 including six diodes. , And is converted to a voltage V by the resistor 31. This voltage V is compared with a reference voltage V ₀ in a comparison circuit 32, and when V is larger than V ₀ , a trip signal TS is output. This OC
If R-H18a is used, it is about 1 ms to 2
Since the trip signal TS can be generated in ms,
The trip signal TS can be output in a short time of about 1/5 to 1/10 as compared with about 10 ms when the overcurrent relay OCR-H having the conventional circuit configuration is used.
S17 can be quickly opened.

Another high-speed overcurrent relay O shown in FIG.
CR-H18b uses three CTs and is called a 3CT system. The OCR-H18b detects a load current from each phase of the three-phase power supply lines R, S, and T to the load via the CT, and rectifies the load current by the full-wave rectifier circuit 30 also including six diodes. The voltage is converted into a voltage V by a resistor 31,
This voltage V is compared with a reference voltage V ₀ in a comparison circuit 32, and is the same as the OCR-H18a in FIG. 3 in that a trip signal TS is output when V is greater than V ₀ , but the difference is that In this configuration, a resistor 33 is connected to a stage preceding the rectifier circuit 30. This resistor 33 can be replaced with another measuring instrument or the like, and the flexibility in use increases.

The high-speed interruption performance when this high-speed overcurrent relay OCR-H18b is used is the same as that in FIG.
FIG. 5 shows the breaking performance when the high-speed overcurrent relay OCR-H18a of FIG. 3 or the high-speed overcurrent relay OCR-H18b of FIG. 4 is used. ₁ to 2 ms from the occurrence of a short circuit accident (t ₀ ) to the generation of the trip signal TS (t ₁ ), and then V
Since it takes about 5 ms before S17 is released (t ₂ ), VS1 is generated in an extremely short time of 6 to 7 ms after the occurrence of the accident.
7 is opened, and the short-circuit current can be suppressed to the rated current value by the current limiting impedance 15. This can reduce the time by 8 to 9 seconds as compared with the case where the conventional OCR-H shown in FIG. 2 is used.

In the above-described embodiment, when any one of the OCR-Hs of the five power generation systems that operate in connection with the commercial power supply system detects an overcurrent in its own system, it outputs a trip signal to shut off the system. However, in order to prevent malfunction of the shut-off device due to noise or the like, another embodiment in which the OCR-H of two or more power generation systems performs a shut-off operation only when an overcurrent is detected. The form can be considered.

This second embodiment is similar to the first embodiment shown in FIG.
The circuit configuration is the same except for the OR circuit 28 in the embodiment. Therefore, the same circuit configuration is omitted,
FIG. 6 shows an example in which only the determination circuit 28a instead of the OR circuit 28 is configured by a logic circuit.

The discrimination circuit 28a includes five AND circuits 41-41.
45 and six OR circuits 51 to 56. Of five systems of the power generation system I~V OCR-H ₁ ~O
Any two of CR-H ₅ but if it detects an overcurrent and outputs a tentative trip signal, it the trip signal TS from the OR circuit 56 is judged is outputted by the determination circuit 28a. The transistor 24,
26 is turned on, and a series of opening operations of the VSs 17 and the VCBs 12 is the same as in the first embodiment shown in FIG.

Since the discrimination circuit 28a shown in FIG. 6 has a complicated circuit configuration, it can be composed of transistors as shown in FIG.

The discriminating circuit 28b includes a series circuit (61 + R) of a transistor and a resistor for each power generation system.
₁ ), (62 + R ₂ ), (63 + R ₃ ), (64 + R
_{4), (65 + R 5} ) was prepared, to connect them in parallel, and a resistor 66 (resistance value r) to the parallel circuit in series, connected in its entirety between the DC power source pn, across the resistor 66 Is compared with the reference voltage V ₀ in the comparison circuit 67. The base of transistor 61 to 65 is connected to the output terminal of the OCR-H ₁ ~OCR-H ₅ each of the power generation system, so as to conduct by the temporary trip signal from OCR-H.

[0036] Now, even if the output of either one system overcurrent relay by OCR-H is overcurrent detection provisional trip signal of the power generation system, the voltage drop V by the resistance 66 by it is smaller than the reference value V ₀ So this trip signal TS
Is not output. In contrast, when the OCR-H in the power generation system having the above two systems (at least 2 systems) overcurrent is detected, the composite current flows through the resistor 66, the voltage drop V by it is greater than the reference value V ₀ Therefore, the trip circuit TS is output from the comparison circuit 67. VS17 and V by this trip signal TS
The opening operation, that is, the shutoff operation of the CB 12 is the same as that described above, and will not be described.

[0037]

As described above, according to the present invention,
In an interconnected operation system of a plurality of gas turbine driven generators and a commercial power supply system, each generator is installed by installing a high-speed cut-off device with excellent high-speed cut-off performance on the power supply system side without using expensive semiconductor switches. It is possible to deal with system accidents without installing each system. As a result, even when a severe accident such as a short-circuit accident occurs on the power supply system side, the probability that the shear pin of the gas turbine is cut due to high-speed interruption can be reduced as compared with the related art. In particular, if a high-speed overcurrent relay that employs a three-phase full-wave rectifier and detects overload by DC approximation is used as an overload detector to detect an overload condition, better high-speed cutoff performance can be obtained. Can be

[Brief description of the drawings]

FIG. 1 shows an electric circuit as an embodiment of a high-speed current limiting device for a gas turbine according to the present invention.

FIG. 2 shows the breaking performance of the high-speed current limiting breaker for a gas turbine according to the present invention.

FIG. 3 shows an electric circuit of a preferred embodiment of a high-speed overcurrent relay OCOCR-H used in a high-speed current limiting circuit breaker for a gas turbine according to the present invention.

FIG. 4 shows an electric circuit of another preferred embodiment of the high-speed overcurrent relay OCR-H used in the high-speed current limiting circuit breaker for a gas turbine according to the present invention.

FIG. 5 shows a preferred overcurrent relay OCR-H according to the invention.
1 shows the shut-off performance of a high-speed current limiting cut-off device for a gas turbine using the same.

FIG. 6 shows a partial circuit configuration of another example of the trip control circuit used in the high-speed current limiting circuit breaker for a gas turbine according to the present invention.

FIG. 7 shows another circuit configuration replacing the trip control circuit shown in FIG.

FIG. 8 is a system diagram of a power generation system using a gas turbine as a driving source.

FIG. 9 is a system diagram of an example of a conventional gas turbine shut-off device.

FIG. 10 shows the breaking performance of a conventional gas turbine breaking device.

FIG. 11 is a system diagram of an example of a conventional high-speed shut-off device for a gas turbine.

[Explanation of symbols]

1-1, 1-2,... 1-5 Gas turbine 2 Reducer 3-1, 3-2,... 3-5 Generator 4 Vacuum breaker (VCB) 5 Shear pin 15 Current limiting impedance 16 Power Fuse 17 Vacuum switch (VS) 18-1, 18-2, ... 18-5 Overcurrent relay (OCR-H) 20, 21 Trip coil 22b Thyristor 23 Contact 24, 26 Transistor 25 Photodiode 27 Auxiliary relay 28, 28a Discrimination circuit 29 Optical fiber 30 Full-wave rectifier circuit 31 Resistance 32 Comparison circuit 41-45 AND circuit 51-55 OR circuit 61-65 Resistance

Claims (7)

[Claims] In a system for interconnecting a plurality of generators driven by a gas turbine and a commercial power supply system, a current-limiting impedance and a vacuum circuit breaker connected in series to a load power supply circuit from a commercial power supply; A vacuum switch connected in parallel with the current-limiting impedance, and a plurality of switches for detecting a load current flowing through a load power supply circuit from the generator for each generator and outputting a trip signal when the detected load current exceeds a predetermined value. And a trip control circuit for opening the vacuum switch in advance of the vacuum circuit breaker in accordance with the trip signal. 2. The high-speed current limiting device for a gas turbine according to claim 1, wherein the overload detector is an overcurrent relay. 3. The high-speed current-limiting device for a gas turbine according to claim 1, wherein the overload detector is an undervoltage relay. 4. The high-speed current-limiting device for a gas turbine according to claim 1, wherein the current-limiting impedance mainly comprises a current-limiting resistance. 5. The high-speed current-limiting device for a gas turbine according to claim 1, wherein the current-limiting impedance mainly comprises a current-limiting reactor. 6. A full-wave rectifier, wherein the overload detector performs full-wave rectification of a load current detected for two or three phases of a three-phase load power supply circuit, and outputs a current value obtained by the full-wave rectification as a voltage. 6. A high-speed overload detector comprising: a comparison circuit that converts the value into a predetermined value, compares the value with a predetermined value, and outputs a trip signal when the value is larger than the predetermined value. High-speed current limiting device. 7. The vacuum control circuit according to claim 1, wherein said trip control circuit opens said vacuum switch and said vacuum circuit breaker in a predetermined order when a trip signal is output from at least two of said plurality of overload detectors. The high-speed current-limiting device for a gas turbine according to claim 1.