JPH0468874B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a synchronous generator islanding detection device, and more particularly to a synchronous generator islanding detection device suitable for detecting islanding during a remote power outage.

In general, it is easy to detect islanding of a generator due to a load interruption within a power plant, but it is not easy to detect islanding when a power plant is healthy and the other end of the power plant is out of load, or is far away. do not have. On the other hand, if the islanding of the generator is not detected accurately, the governor will not be able to properly switch from load damping to no-load damping, and the generator will not be able to operate stably at its speed during islanding. . Furthermore, secondary regulators such as automatic water level regulators and automatic power factor regulators are not excluded during independent operation, resulting in problems such as operation with frequency and voltage deviating from reference values.

Therefore, in order to detect isolated operation of a generator in the event of a disconnection in a remote area, conventionally, as shown in FIG.
2. Main transformer 13, voltage transformer 15, voltage current transformer 16 of the high voltage side circuit of the main transformer 13, which is connected to the power transmission line 2 via the high voltage side disconnector 14.
Detection relays 17 such as active power relays, current relays, or frequency relays are installed to perform detection. Incidentally, the shield disconnectors 18 and 19 provided in parallel with the parallel shield disconnector 12 of the power plant 1 are the shield disconnectors for the station circuit connected to the non-power source load and the distribution line disconnectors. .

However, in this method, the detection relay 17 may change due to changes in active power, current, etc. during operation, or changes in the rise in generator frequency when the load is interrupted depending on the load condition at that time. There were problems in that it was difficult to set up and it was not possible to obtain satisfactory detection results.

In order to eliminate such problems, transfer trip devices 4 and 5 are provided at the power station 1 and the opposite end electric station 3,
Conventionally, a transfer trip transmission line 6 is used to connect the two, and a disconnection signal from the opposite end disconnector 31 is transferred to the power plant 1, thereby detecting islanding.

According to this method, islanding operation can be detected reliably, but a transfer trip transmission line 6 must be installed between the power plant 1 and the opposite end power plant 3, which has the disadvantage of increasing equipment costs. It was hot.

SUMMARY OF THE INVENTION An object of the present invention is to provide a simple and inexpensive synchronous generator islanding detection device that can more accurately detect isolated operation in the event of a power outage over a distance.

In order to achieve this object, the present invention connects the synchronous generator 11 to the main transformer 13 via a parallel shunt breaker 12, as shown in FIGS. 2 and 3, and In a device for detecting standalone operation of the synchronous generator 11 of a power plant connected to the power grid via a power supply system, the automatic voltage regulator 23 of the synchronous generator 11 is always supplied with an invalid voltage of a certain value or more. a reactive power adjustment device 25 that issues a command to generate electric power; a detection device 26 that detects when the reactive power or reactive current on the high voltage side of the main transformer 13 has become almost zero; and the synchronous generator 11.
A circuit 12a that detects islanding when both the conditions for turning on the parallel shield breaker 12 and the detection condition that the reactive power or reactive current on the high voltage side of the main transformer 13 has become almost zero are satisfied; 41, 26b, 41b,
42, 42a.

Alternatively, as shown in FIG. 5 and FIG.
In a device for detecting islanding of the synchronous generator 11 of a power plant connected to the main transformer 13 via the main transformer 13 via the high voltage switch 14 and further connected to the grid via the high voltage switch 14, the automatic voltage of the synchronous generator 11 is detected. A reactive power adjusting device 25 that issues a command to the regulator 23 to always generate reactive power of a certain value or more from the synchronous generator 11, and a reactive power adjusting device 25 that issues a command to the regulator 23 to always generate reactive power of a certain value or more, and a reactive power or reactive current on the high voltage side of the main transformer 13 is almost zero. a detection device 26 for detecting the overvoltage of the terminal voltage of the synchronous generator 11; an overvoltage detection device 27 for detecting the overvoltage of the terminal voltage of the synchronous generator 11; 3. A detection condition that the reactive power or reactive current on the high voltage side of the transformer 13 has become almost zero, and a detection condition that the terminal voltage of the synchronous generator 11 is overvoltage.
Circuit 1 that detects islanding when two conditions are met
2a, 41, 27a, 26b, 41a, 42, 4
2a.

Hereinafter, the present invention will be explained with reference to the drawings.

FIG. 2 shows a configuration diagram of an islanding detection device for a synchronous generator according to an embodiment of the present invention, and in the figure, the same reference numerals as in FIG. 1 indicate the same or corresponding parts.

Typically, the power plant 1 is provided with an instrument transformer 21, an instrument current transformer 22, an automatic voltage regulator 23, and an excitation thyristor 24 as excitation devices for the generator 11. Therefore, in this embodiment, in addition to these configurations, the automatic voltage regulator 23
A reactive power regulator 25 that functions as ) 26 is provided.

The reactive power regulator 25 is connected to the parallel shear disconnector 1
2 is turned on, the function is activated, _and as shown in FIG.
give the necessary signals to.

In other words, the reactive power adjustment operation at this time is:
As shown in Figure 3, (a) Q=a operation, (b) Q=a+
bP operation, (c) Q = bP operation, etc. are possible, and in the cases of (a) and (b), the reactive power Q _A necessary for detection can be secured, but
In the case of (c), if the load falls below a certain value, the reactive power Q _A necessary for detection cannot be secured. Therefore,
In the case of (c), the reactive power regulator 25 detects A where the reactive power Q _A necessary for detecting islanding operation cannot be secured, and as shown by the chain line, the range of the active power P _A and the reactive power Q _A are kept constant. functions to maintain

FIG. 4 shows a configuration diagram of an islanding detection circuit according to an embodiment of the present invention, where 41 is a time-limited relay and 42 is an auxiliary relay. Further, 12a is an auxiliary a contact of the parallel shunt breaker 12, 26b is a b contact of the reactive power relay (or current relay) 26, and 41
A is the a contact of the time limit relay 41, and 42a is the a contact of the auxiliary relay 42.

The islanding detection device of this embodiment is configured as described above, and when the system is paralleled with the parallel sheath disconnector 12 and the high voltage side sheath disconnector 14 turned on, the reactive power regulator 2
5 is activated, and the generator 11 is activated by the automatic voltage regulator 23.
The excitation of is controlled, and the generator 11 always generates reactive power greater than Q _A. Further, when the parallel sheath breaker 12 is inserted, its auxiliary contact 12a shown in FIG. 4 is closed. As a result, time-limited relay 4
1 is activated, and the contact 41a thereof closes after the time required to generate the reactive power necessary for detection has elapsed since the parallel shield breaker 12 was turned on. On the other hand, the reactive power relay (or current relay) 26 connects the generator 11
As a result of detecting the reactive power generated from the
When 41a closes, its contact 26b is open, so auxiliary relay 42 does not operate.

In this state, if the opposite end sheath breaker 31 of the opposite end electric station 3 is suddenly disconnected or the high voltage side sheath breaker 14 is suddenly disconnected, the high voltage side reactive power of the main transformer 13 becomes approximately zero. As a result, the operation of the reactive power relay (or current relay) 26 is stopped.

Therefore, the contact 26b closes, the auxiliary relay 42 operates, and the independent operation signal is output from the contact 42a. This signal causes the speed governor to be switched from load damping to no-load damping, and to exclude secondary regulators such as an automatic water level regulator and an automatic power factor regulator.

In this way, in this embodiment, islanding is detected by constantly generating reactive power equal to or higher than a certain value Q _A from the generator 11 and monitoring this with the reactive power relay (or current relay) 26. Therefore, it is possible to accurately detect a disconnection from a distance, and when a disconnection occurs, the generator 11 can be operated in a state appropriate to the load at that time.

By the way, if the reactive power relay (or current relay) 26 only detects almost zero reactive power as in the above embodiment, the reactive power will transiently become almost zero due to fluctuations in the grid voltage during parallel operation. , there is a risk of erroneously detecting the independent operation of the generator 11. However, in that case, as shown in FIG.
By providing an overvoltage detection relay 27 for detecting overvoltage during reactive power operation and configuring the islanding detection circuit as shown in FIG. 6, detection accuracy can be improved.

That is, when the opposite end or disconnector 31 is disconnected and the reactive power becomes almost zero, the reactive power regulator 25 acts in a direction to strengthen the excitation of the generator 11, and as a result,
The terminal voltage of generator 11 increases. This is detected by the overvoltage detection relay 27, and the a contact 27a and the b contact 2 of the reactive power relay (or current relay) 26
6b operates the auxiliary relay 42. This makes it possible to more reliably detect isolated operation when the vehicle is far away or disconnected.

In the above embodiment, an example was explained in which the reactive power relay (or current relay) 26 was provided on the high voltage side of the main transformer 13, but even if it is provided on the low voltage side, the same effects as in the above embodiment can be obtained. can get.

In addition, the reactive power regulator 2 in the above embodiments
In place of 5, the automatic reactive power regulator (AQR), which is normally used for reactive power control or power factor adjustment control of generators in power plants, or the automatic power factor regulator (APFR), which is normally used for reactive power control or power factor adjustment control of generators, or the automatic power factor regulator (APFR), can be used to control the override required to detect islanding. Power Q _A
It can also be used as a device for commanding the generation of

Furthermore, in the above embodiments, an example of detecting isolated operation within a station has been described, but it goes without saying that the present invention is also applicable to detecting isolated operation of a generator with a load.

As described above, according to the present invention, without installing expensive equipment such as a transfer trip device or a transfer trip transmission line, the device can be easily, inexpensively, and reliably installed using equipment normally installed in a power plant. A synchronous generator islanding detection device capable of detecting islanding of a generator during a remote power outage can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional synchronous generator islanding detection device, Fig. 2 is a block diagram of a synchronous generator islanding detection device according to an embodiment of the present invention, and Fig. 3 is a block diagram of a synchronous generator at that time. FIG. 4 is a configuration diagram of an islanding detection circuit according to an embodiment of the present invention,
FIG. 5 is a block diagram of a synchronous generator islanding detection device according to another embodiment of the present invention, and FIG. 6 is a block diagram of its islanding detection circuit. DESCRIPTION OF SYMBOLS 1... Power plant, 2... Transmission line, 3... Phase end electrical station, 4, 5... Transfer trip device, 6... Transfer trip transmission line, 11... Generator, 12... Parallel cable Disconnector, 13... Main transformer, 14... High voltage side disconnector, 15, 21... Instrument transformer, 16, 2
2... Instrument current transformer, 17... Detection relay, 1
8, 19...Shield breaker, 23...Automatic voltage regulator, 24...Excitation thyristor, 25...Reactive power regulator, 26...Reactive power relay (or current relay), 27...Overcurrent Detection relay, 31... Opposite terminal disconnector, 41... Time limit relay, 42... Auxiliary relay.

Claims (1)

[Claims] 1. Independent operation of the synchronous generator in a power plant in which the synchronous generator is connected to the main transformer via a parallel shield and disconnector, and further connected to the grid via a high-voltage shield and disconnector. The detecting device includes: a reactive power adjustment device that issues a command to an automatic voltage regulator of the synchronous generator to cause the synchronous generator to always generate reactive power of a certain value or more; a detection device that detects when reactive power or reactive current has become almost zero; and conditions for turning on a parallel switch and disconnector for the synchronous generator;
A synchronous generator comprising: a detection condition that reactive power or reactive current on the high voltage side of the main transformer has become almost zero; and a circuit that detects islanding when both conditions are satisfied. Islanding detection device. 2. In a device for detecting islanding of the synchronous generator of a power plant in which the synchronous generator is connected to the main transformer via a parallel switch and disconnector and further connected to the grid via a high voltage switch and disconnector, a reactive power adjustment device that issues a command to an automatic voltage regulator of a synchronous generator to cause the synchronous generator to always generate reactive power of a certain value or more; a detection device for detecting that the voltage has become almost zero; an overvoltage detection device for detecting an overvoltage of the terminal voltage of the synchronous generator; and a condition for turning on a parallel circuit breaker for the synchronous generator;
Islanding is detected when three conditions are satisfied: a detection condition that the reactive power or reactive current on the high voltage side of the main transformer has become almost zero, and a detection condition that the terminal voltage of the synchronous generator is overvoltage. An islanding detection device for a synchronous generator, comprising a circuit.