JPH06276662A - Back-up protective relay device for generator - Google Patents

Abstract

PURPOSE:To make it possible to set a distance relay coordinated with a protective equipment on the power transmission line side by changing the value of an input voltage of the distance relay by using a resistor depending on the operating conditions of other generators. CONSTITUTION:If a plurality of generators T, 8 and 9 are connected to a power transmission bus 3, a current 12 decreases so that an impedance 2 seen from the distance relay 10 becomes larger than the line impedance up to the actual short-circuit point. At this time, among the inputs of short-circuit back-up protection distance relay 10, the voltage of the distance relay 10 is reduced by resistors 25 to 27 having respectively different resistance values switched by auxiliary contacts 19 to 20 of the generators 7, 8 and 9 in an input circuit of voltage (PT secondary voltage) as generator information, by which the value of generator voltage V seen from the distance relay is virtually made smaller in response to the change in T1, and the result V/11 is made constant. In this way, by making constant the impedance seen from the distance relay 10, the protection range can be made constant regardless of the number of operating units of generators.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suitable generator back-up protection relay device by a distance relay in an electric installation composed of a single power transmission bus and a plurality of generators connected thereto.

[0002]

2. Description of the Related Art In the case of a short circuit, a distance relay judges whether or not the line impedance up to the short circuit point seen from the distance relay is within a protection range by comparing it with a preset impedance.

In a conventional power generator back-up protection device using a distance relay, when another generator is operating, it acts as an intervening power source, and the line impedance up to the short-circuit point as seen from the distance relay apparently changes. The protection range of the relay changed and was not constant, so that it was not possible to settle in coordination with the protection device on the transmission line side in all operating conditions of the generator.

[0004]

When a generator other than the generator is in operation, the apparent impedance seen from the distance relay changes, so the distance relay is protected on the transmission line side in a specific operating state of the generator. Even if the range is determined and the distance relay is settled in cooperation with the protection device on the transmission line side, the protection range is changed in other operating conditions and the protection device on the transmission line side cannot be coordinated.

[0005]

[Means for Solving the Problems] The apparent generator voltage is changed by changing the input voltage value of the distance relay by using a resistor according to the operating state of another generator (that is, the presence or absence of an intervening power source). By doing so, the change in impedance up to the short-circuit point due to the operating state of the generator other than the applicable generator is corrected, and as a result, the fluctuation of the protection range is prevented and the transmission line Set the distance relay in coordination with the protection device on the side.

[0006]

According to the present invention, the distance relay can be set so that the protection range is constant regardless of the operating state of the generator.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows the configuration of electric equipment.

A distance relay 10 for protection against short circuit of the generator 7.
The front protection of the line impedance from the distance relay 10 to the F1 point 2 (that is, the front impedance) is based on the ratio V / I1 of the outlet voltage V11 of the generator 7 and the current 12 of the generator 7 at the time of three-phase short circuit at the F1 point 2. ) Is detected and is smaller than the set impedance, that is, the short-circuit point 2 is within the protection range, and a countermeasure such as a generator trip is taken.

Here, in the electric equipment in which a plurality of generators are connected to the power transmission bus 3 as in the embodiment, the generator 7
When any of the generators 8 and 9 other than the above or both are operating, the current 12 is the series impedance of the generator 7, the generator 8 and the parallel impedance of the generator 9 and the transmission line impedance up to the point F1. It is shunted by the circuit. Therefore, as the number of generators operating in parallel increases, the current 12 decreases,
V / I1 at this time (impedance seen by the distance relay)
Is larger than the line impedance up to the actual short-circuit point.

FIG. 2 shows a voltage and current input circuit of the distance relay 10 for protection against short circuit.

Of the inputs of the distance relay 10, different resistance values are switched by the auxiliary contacts 19 to 20 of the generator breakers 7, 8 and 9 to the input circuit of the voltage (PT secondary voltage) which is the generator information. Distance relay 1 with resistors 25-27
The voltage of 0 is reduced to correspond to the change of I1, and the value of the generator voltage V as seen from the distance relay is apparently made small, so that V / I1 is made constant and the impedance seen from the distance relay 10 is made constant. By doing so, the protection range can be made constant regardless of the number of operating generators.

[0013]

According to the present invention, the range of protection by the distance relay (44 relay) is constant irrespective of the operating state of the generators (the number of parallel operating units), and the backup device can cooperate with the protective device on the transmission line side. It can be a protection device.

[Brief description of drawings]

FIG. 1 is an electrical system diagram of an embodiment of the present invention.

FIG. 2 is a sequence circuit diagram of a distance relay.

[Explanation of symbols]

7 ... Generator, 10 ... Generator protection protection distance relay, 15 ...
Generator PT, 16 ... Generator CT, 17 ... Current coil of distance relay, 18 ... Voltage coil of distance relay, 19 to 20
… Auxiliary contacts of generator breaker, 21-24… Auxiliary relay,
25-27 ... Resistance for voltage adjustment.

Claims (1)

[Claims] 1. An electric facility comprising a single power transmission bus and a plurality of generators connected to the single power transmission bus,
In order to prevent the range of protection of the distance relay including up to a part of the transmission line installed as backup protection of the short circuit protection of the generator from changing according to the operating state of another generator, the distance relay is included. A protective protection relay device for a generator, characterized in that the protection range is made constant by changing the voltage input of the device using a resistor.