JPH09135527A - Over current protective relay with settling pattern automatic changing-over function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To change a settled value easily and maintain the optimum protective environment to correspond to the power supply condition in an over current protective relay which is installed in a receiving and transforming facility provided with an emergency generator placed side by side with a commercial power supply. SOLUTION: A settling pattern 12 which can be set and changed on electric signals, etc., from outside and which is used when power is supplied by a commercial power supply and a settling pattern 13 which is used when power is supplied by an emergency generator are built in an over current protective relay 11. The excess current protective relay 11 is also provided with a power supply condition judging circuit 14 which determines whether the power supply of a receiving and transforming facility is a commercial power supply or emergency generator and a changeover switch 15 which selects a proper settling pattern according to the power supply judged by the power supply condition judging circuit 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protective relay for protecting power receiving and transforming equipment, and more particularly to an overcurrent protective relay.

[0002]

2. Description of the Related Art A protective relay constantly monitors the normality and abnormality of equipment in order to protect the power receiving and transforming equipment. If an abnormality is detected, the equipment is promptly disconnected from the electric circuit. It issues a command. Overcurrent protection relay
It distinguishes between normal current (rated current) and abnormal overcurrent (overload or short circuit). The current technology of a general overcurrent relay is generally as follows.

(1) A set value is set by a dial, a tap or the like of the relay body. (2) There is only one set value.

[0004]

A power receiving and transforming facility equipped with an emergency power generator is constructed as shown in FIG. 3, for example. FIG.
In the above, AC power from a commercial power supply (not shown) is supplied to a load (not shown) via the circuit breaker 1, the AC bus 2, the circuit breakers 3, 4, 5, 6 and the transformer 7. An emergency generator G is connected to the AC bus 2 via a circuit breaker 8.
CT is a current transformer and OC is an overcurrent relay. In FIG. 3, transformers, loads, etc. connected to the circuit breakers 3, 4, 6 are not shown.

The power receiving and transforming equipment constructed as shown in FIG. 3 has the following problems. (1) Protection is possible during commercial power reception, but not when power is being supplied from the emergency generator G. (Reason) In the case of FIG. 3, generally, the short-circuit current Ic at the time of commercial power reception is large. For example, when the short-circuit current Ic is set to 10000 A, the short-circuit current Ic is detected and settled so as to operate in about 0.1 seconds or less. . On the other hand, when power is supplied to the emergency generator, the short circuit current I _G is small due to the impedance of the generator,
For example, in the case of 700 A, the settling is 100 as described above.
If it is set to 00A for 0.1 second, 700A cannot be determined to be abnormal (short circuit).

(2) It is difficult to settle and change quickly when power is supplied to the emergency generator. (Reason) In order to solve the problem of the above item (1), if an attempt is made to change to a settling value that can detect the short-circuit current 700A at the time of power supply to the emergency generator, it is difficult to realize due to the following points.

(2-1) It is impossible to predict when the emergency generator will operate. That is, it is unknown when the commercial power supply will fail. (2-2) When there are many relays, it is very complicated and has a limit to manually change the set value. (2-3) The settling value is preferably changed when the circuit has no voltage, but the time when the circuit has no voltage is extremely short, 10 to 40 seconds.

The present invention has been made in view of the above points, and an object thereof is to make it easy to change a settling value and to maintain an optimum protection environment corresponding to a power supply state, with an overcurrent protection relay having a settling pattern automatic switching function. To provide.

[0009]

In order to achieve the above object, the present invention provides: (1) an overcurrent protection relay provided in a power receiving and transforming facility equipped with an emergency generator installed in parallel with a commercial power source, Built in the overcurrent protection relay, it can set and change by external electric signals etc. and settling patterns, and determine whether the power status of the power receiving and transforming equipment is commercial power or emergency generator. A power source state determining circuit, and a switching unit for performing settling by switching the plurality of settling patterns to an appropriate settling pattern according to the power source determined by the power source state determining circuit,
(2) The emergency generator is characterized by being a generator capable of sustaining a short-circuit current.

(3) When the power supply state determination circuit determines that the power supply state is, for example, the emergency generator, the switching unit switches the settling pattern to the settling pattern for the emergency generator. Therefore, even when a short-circuit current smaller than the short-circuit current during commercial power reception flows, this can be determined to be abnormal. Therefore, the optimum protection environment corresponding to the power supply state is maintained.

The setting and changing of the settling pattern can be freely performed from the outside. Further, the settling pattern can be automatically switched to the optimum one according to the power supply state without manual operation. Therefore, it is possible to remarkably save labor.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. According to the present invention, the overcurrent relay has two built-in settling patterns in advance, that is, a set pattern at the time of commercial power reception and an emergency generator power supply, and by properly using these patterns, optimum protection is achieved even in different power supply states. I was able to do it.

The switching of the two patterns of settling can be performed by an electric signal from the outside, so that the change of the power supply state (commercial → emergency generator power supply, emergency generator power supply → commercial) can be performed. It is possible to detect and automatically maintain the optimum protection state without human intervention.

[0014]

FIG. 1 shows an embodiment of the present invention, in which an overcurrent protection relay 11 has different settling patterns 12,
13 is built in. These settling patterns are preset and can be changed by an external electric signal. The settling pattern 12 (A settling pattern) is a settling pattern for protection during commercial power reception as shown in FIG. 1B, and the settling pattern 13 (B settling pattern) is as shown in FIG. 1C, for example. In addition, it is a settling pattern for protection during power supply to the emergency generator. Reference numeral 14 is a power supply state determination circuit that detects a change in the power supply state of the power receiving and transforming facility and determines whether the power supply state is a commercial power source or an emergency generator. Reference numeral 15 is a changeover switch for switching the settling patterns 12 and 13 to an appropriate settling pattern in accordance with the power source determined by the power source state determination circuit 14.

When the device configured as described above is applied to a power receiving and transforming facility, for example, if the power supply is switched from commercial to emergency generator, the power supply state determination circuit 14
It is determined that the power supply state is the emergency generator. Therefore, the changeover switch 15 is changed over to the setting pattern 13 side,
The overcurrent protection relay 11 is settled to the settling pattern 13 for supplying power to the emergency generator shown in FIG. 1 (c). As a result, a short-circuit accident occurs when power is supplied to the emergency generator G.
Even if a short-circuit current of 0 A flows, the overcurrent protection relay 11 responds to this reliably, and protection such as disconnecting the circuit breaker is performed.

If the emergency generator G is a generator capable of sustaining a short-circuit current, for example, even if a short-circuit accident occurs at the portion marked with X in FIG. It is not necessary to shut off the circuit breaker 8 of (1), and the circuit breaker 21 can be shut off to promptly remove only the accident (short circuit) portion (selective shut-off). In FIG. 2, 8, 21, 22, and 23 are circuit breakers.

In this way, the optimum protection environment corresponding to the power supply state is maintained. Further, the settling pattern can be automatically and optimally switched according to the power supply state without manual operation.
Therefore, even when there are a large number of relays, the labor can be remarkably saved.

The settling pattern built in the overcurrent protection relay is not limited to two but may be three or more.

[0019]

As described above, according to the present invention,
A power supply that incorporates multiple settling patterns that can be set and changed by external electrical signals into the overcurrent protection relay to determine whether the power receiving and transforming equipment is in commercial power or emergency power generator Since a state determination circuit and a switching unit for switching the plurality of settling patterns to an appropriate settling pattern according to the power source determined by the power supply state determination circuit and performing settling are provided, the following excellent effects are obtained. To be

(1) An optimum protection environment corresponding to the power supply state can be maintained.

(2) If short-circuit current can be maintained in the generator body even during power supply to the emergency generator, only the accident (short-circuit) point can be promptly removed, so-called selective cut-off protection is possible.

(3) Due to the above (2), it is possible to continue the power supply except for the accident location even when the emergency generator power is supplied, and the accident does not spread to other healthy load side.

(4) Since the settling pattern can be automatically set, changed, and switched, labor can be saved.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention, (a) is an overall block diagram, (b) is a characteristic diagram of a settling pattern used during commercial power supply, and (c) is a settling pattern used during emergency generator power supply. Characteristic diagram of.

FIG. 2 is a single-line connection diagram of a power system for explaining the effect of the present invention.

FIG. 3 is a single wire connection diagram showing an example of conventional power receiving and transforming equipment.

[Explanation of symbols]

 1,3,4,5,6,8,21,22,23 ... Circuit breaker 2 ... AC bus 7 ... Transformer 11 ... Overcurrent protection relay 12, 13 ... Settling pattern 14 ... Power supply state determination circuit 15 ... Changeover switch OC ... Overcurrent relay CT ... Current transformer G ... Emergency generator

Claims (2)

[Claims] 1. An overcurrent protection relay provided in a power receiving and transforming facility equipped with an emergency generator installed in parallel with a commercial power supply, which is built in the overcurrent protection relay and is set and changed by an external electric signal or the like. Depending on the power source determined by the power source status determination circuit, a plurality of settling patterns that can be set, a power status determination circuit that determines whether the power status of the power receiving and transforming equipment is commercial power or an emergency generator, An overcurrent protection relay with an automatic settling pattern switching function, comprising: a switching unit for switching the plurality of settling patterns to an appropriate settling pattern for settling. 2. The overcurrent protection relay with settling pattern automatic switching function according to claim 1, wherein the emergency generator is a generator capable of sustaining a short-circuit current.