JPH0222610B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a system separation device using an underpower relay.

An example of a system equipped with a conventional system separation protection circuit is explained with reference to FIG. 1. 1 is a power company's substation equipment with a large-capacity power source, which includes a power source 11, a power line disconnector 12, and a transmission line disconnector. 13 and 14 to supply power to the power receiving equipment 2 and 3 of each consumer. The consumer power receiving equipment 2 includes a power receiving sheath disconnector 21 and a transformer 2
7. Transformer secondary breaker 22, busbar breaker 2
3. It is composed of a private generator connection and disconnector 24, distribution line disconnectors 25 and 26, a private generator 28, etc., and regular operation in this system is performed by connecting the electric power company's power supply 11 and the private generator 28. Due to parallel operation, loads A and B are
It supplies electricity to the

When such a system is operated in parallel, the electric power company power supply 11
If the power transmission is stopped, the entire load will be borne by the private generator power supply 28, and if the total operating load is too large for the generator output capacity, the private generator 28 will be overloaded and may shut down. The overcurrent protection will shut off the power supply 24, resulting in a power outage for the entire facility.

Therefore, in order to prevent such a total power outage, conventionally, an instrument transformer 29 and an instrument current transformer 30 are provided at the receiving power supply entry point of the consumer power receiving and transforming equipment 2, and an underpower relay 31 is connected to the secondary side of the instrument transformer 29 and instrument current transformer 30. When the power shortage is detected and the received power value decreases below a certain value, it is determined that the electric power company's power supply 11 has stopped transmitting power, and the load B is continued to be operated to the extent that it is balanced with the output capacity of the private generator 28. bus line disconnector 23
The system connected to the electric power company's power source 11 and the system connected to the private generator 28 are separated. In this case, the setting value of the underpower relay 31 is a value close to the minimum load amount that can be considered during steady operation of the equipment.

FIG. 2 shows a conventional system separation protection circuit using an underpower relay, which includes a switch 41 set to use underpower protection between DC control power supplies P and N, an operating contact 31-b of the underpower relay 31, and an auxiliary relay 42. are connected in series, and the operating contact 42-a of the auxiliary relay 42 is inserted into the tripping signal circuit of the breaker 23. That is, when the switching switch 41 for setting the use of underpower protection is set to the use side, when the underpower relay 31 (see Fig. 1) operates (returns), its contact 31-b closes. The auxiliary relay 42 is energized, its contacts 42-a are closed, and the busbar breaker 23 is tripped, separating the electric power company power supply 11 and the private generator power supply 28, and disconnecting the load B of the private generator system. The vehicle continues to operate. The switching switch 41 for setting the use of insufficient power protection is used to exclude the tripping signal of the busbar breaker 23, and is used when the equipment is connected to the power company power supply 11 from a total power outage state, or when the equipment is connected to a private generator. 2
When drawing in parallel to the electric power company power supply 11 from the standalone operation in step 8, switch to the unused side to enable the bus line and disconnector 23 to be turned on, and confirm that a certain amount of power has been drawn. After that, it is switched to the user side and placed on standby for grid separation when the power company shuts down.

In this way, the conventional grid separation protection circuit, when the equipment draws in the electric power company's power supply 11 from a total power outage, turns on the power receiving system breakers 21 and 22, and then before turning on the busbar breakers 23. The procedure is to set the switching switch 41 for setting the use of insufficient power protection to the non-use side. Therefore, if this is neglected, the bus bar and disconnector 23 cannot be closed. Furthermore, if the switching switch 41 is left in the unused side while the electric power company power source 11 and the private generator 28 are operating in parallel, it will be impossible to separate the system when the electric power company power supply is stopped, resulting in a complete power outage of the equipment. I'm getting used to it. Furthermore, if a short circuit occurs at, for example, point F in the power company's substation equipment 1, the system voltage will drop significantly due to the short circuit reactive current. The receiving power of the power receiving and substation equipment 2 also decreases significantly, so the relay 31 also operates to compensate for the lack of power, and the busbar disconnector 23
may trip unnecessarily.

The purpose of the present invention is to supply power to a power distribution system that ensures system separation when power is stopped from being transmitted from a power company, and eliminates problems caused by troublesome work or operational errors when drawing in power from a power company from a state of total power outage. It is an object of the present invention to provide a system separation device that is effective for stabilization, and at the same time, to provide a system separation device that can prevent unnecessary system separation operations due to short circuits on the power company side.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 3 shows an embodiment according to the present invention, and the symbols 1 to 3, 11 to 14, and 21 to 31 shown in the figure are the first
It is the same as the part indicated by the same reference numeral in the figure, and an underpower relay 31 is provided on the secondary side of the instrument transformer 29 and instrument current transformer 30 provided at the power receiving point of the consumer power receiving and transforming equipment 2. The difference from FIG. 1 is that a power relay 32 and a short-circuit direction relay 33 are provided. The power relay 32 is in the form of an induction disk and has an inverse timing characteristic, and operates when the power received from the electric power company power source 11 exceeds the set power value of the power relay 32, and the set value is the steady state of the grid. This is the minimum expected power receiving power during operation, and operation continues when the power receiving power is greater than this minimum value. On the other hand, the operating value of the underpower relay 31 shall be set as small as possible, and the short-circuit direction relay 33 is for detecting reactive power flowing into the power company's substation equipment 1, and is activated when a short circuit accident occurs in the power company's substation equipment 1. It is something to do.

FIG. 4 shows a system separation protection circuit, in which a contact 32-a of a power relay 32 is connected between DC control power supply P and N.
and the off-day timer 43 are connected in series, and P
A tripping control relay 44 having an on-day function is connected between -N and the B contact 33-b of the short-circuit direction relay 33, the B contact 31-b of the underpower relay 31, and the A contact 43-a of the off-day delay timer 43 in series. At the same time, the auxiliary contact 2 of the busbar breaker 223 is connected between the power supply P and the upper end of the drawer control relay 44 in the drawing.
3-a and a contact 44-a of tripping control relay 44 ₁
A holding circuit is constructed by connecting these in series. Another contact 44-a ₂ of the tripping control relay 44 is inserted in series into the tripping signal circuit of the bus-bar breaker 23.

Next, the operation of the above circuit will be explained. The minimum value of power received from the electric power company power supply 11 during steady operation (underpower relay 3
1 is the reset value) or higher, power relay 3 is activated.
2 continues to operate, and since its contact 32-a is closed, the off-day timer 43 is energized to prepare for power shortage protection.

If the electric power company power supply 11 stops in the standby state for power shortage protection (while the off-day timer 43 is operating), the power shortage relay 31 operates and its contacts 31
-b is closed, and at the same time the power relay 32 returns and its contact 32-a opens, but by setting the off-day time of the off-day timer 43 to be somewhat longer than the on-day timer time of the tripping control relay 44, the tripping control relay 44 operates and its contact 4
4-A ₂ outputs a tripping command to the bus line disconnector 23.

In addition, a self-holding circuit in which the contact 44-a ₁ of the trip control relay 44 and the auxiliary contact 23-a of the bus-bar break switch 23 are connected in series is closed, and a trip command is output with a sufficient signal time. be done. On the other hand, electric power company power supply 1
1 draws power again from the stopped state, the contacts of the off-day timer 43 have returned to open, and the excitation circuit of the trip control relay 44 has become invalid, so the power receiving system's disconnectors 21 and 22 are turned on. It is also possible to insert the rear bus bar and disconnector 23. Further, when the drawn-in power recovers to the operating range of the power relay 32, the off-day timer 43 operates and enters a standby state to protect against power shortage. In addition, if a short circuit accident occurs in the electric power company's substation equipment system during the standby state of power shortage protection, the short circuit direction relay 33 is activated, and its contacts 33
-b opens, the excitation circuit of the tripping control relay 44 is disabled, and the breaker 23 is not tripped unnecessarily. In this case, in the tripping control relay 44, even if the underpower relay 31 operates and its contacts 31-b close in the event of the short circuit accident, the short-circuit direction relay 33 operates and its contacts 33-b open, excluding underpower protection. Both contacts 33-b, 31
-b operation time coordination is performed.

In addition, if the load amount of the received power from the electric power company power supply 11 is gradually reduced from the operating range of the power relay 32 by human operation during steady operation, the load is reduced before the value at which the undervoltage relay 31 operates. At the time of operation, the power relay 32 is reset, the off-day timer 43 is also reset, and its contact 43-a is opened, so that underpower protection is excluded and the busbar breaker 23 is not unnecessarily tripped.

As described above, according to the first invention, the power relay continues to operate during steady operation to maintain power shortage protection in a standby state, and when power transmission from the electric power company's substation equipment is stopped, the power shortage relay operates. As a result, system separation was performed, and even when the power company's power was brought in from a complete power outage, the power relay was restored, so power shortage protection was excluded, making it difficult to turn on the busbars and disconnectors. A stable power supply from the power distribution system can be expected without the troublesome work of setting undervoltage protection on the use side and the non-use side and operational errors like in conventional devices using a switching switch.

According to the second invention, in the event of a short-circuit accident in the power company's substation equipment, the short-circuit direction relay operates, thereby excluding power shortage protection and preventing unnecessary tripping of the busbar or disconnector. A stable power supply can also be expected.

[Brief explanation of drawings]

Figure 1 is a system diagram of power receiving equipment equipped with a conventional system separation protection circuit, Figure 2 is a wiring diagram of the same system separation protection circuit, and Figure 3 is a system diagram of power receiving equipment equipped with a system separation protection circuit according to the present invention. FIG. 4 is a wiring diagram showing an embodiment of the same system separation protection circuit. 1...Power company substation equipment, 2...Power receiving equipment, 2
3...Bus line disconnector, 28...Private generator, 3
1...Underpower relay, 31a...B contact of underpower relay, 32...Power relay, 32-a...
A contact of power relay, 33...Short-circuit direction relay,
33-b...B contact of short-circuit direction relay, 43...
Off-day timer, 43-b...A contact of off-day timer, 44...Tripping control relay, 44-
a ₂ ...A contact of the tripping control relay.

Claims (1)

[Scope of Claims] 1. A system that is installed in a power receiving facility that is provided with a busbar or disconnector that is closed during normal operation between a power supply system from a power company and a power supply system using a private generator, and that transmits power from the power company. In a system separation device that performs system separation by tripping the busbar breakers and disconnectors when stopped, a power relay that operates when the power value of the power transmitted from the power company exceeds a minimum value expected during steady operation; , an underpower relay that detects and operates when the power transmission power becomes lower than a return power value of the power relay, and an underpower relay that operates under the condition that the detection operation of the underpower relay and that the power relay is within a certain period of time after recovery. and a tripping control relay that gives a tripping command to the busbar and disconnector. 2. Installed in power receiving equipment that is equipped with a busbar or disconnector that is closed during normal operation between the power supply system from the electric power company and the power supply system using a private generator, and when the power transmission from the electric power company is stopped, the busbar is closed. In a system separation device that performs system separation by tripping a disconnector or
A power relay that operates when the power transmitted from the electric power company exceeds a minimum value expected during steady operation, and an underpower relay that detects and operates when the power transmitted becomes a value lower than the return power value of the power relay. , a short-circuit direction relay that detects a short-circuit accident that occurs externally from the power receiving point from the electric power company; the inoperation of the short-circuit direction relay; the detection operation of the underpower relay; and the fact that the power relay is within a certain period of time after recovery. and a tripping control relay that operates as an AND condition and gives a tripping command to the bus line disconnector after a certain period of time.