JPS61231840A - Main bus panel for measurement - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an improved main bus board for measurement that supplies power to measurement and control equipment in various plants such as nuclear power plants.
It's about Yu.

"Technical Background of the Invention" Nuclear power plants and other various plants1 use an extremely large number and variety of measuring instruments and control equipment, and their driving sources and signal transmission are performed electrically. is the majority.

Moreover, the stability of this power supply voltage and the reliability of the circuit (both of which are directly reflected in the accuracy and operation of the measuring instruments and control equipment driven by it, are extremely important for plant operation).

Conventionally, power receiving circuit breakers 2a and 2, which are power receiving switchgears that receive alternating current from the switchboards 1m or 1b of the two systems and are interlocked with each other, are installed as shown in Figure 2 (2).
b, a transformer 3 as a means for changing the voltage and insulating it from the power supply circuit, and distribution circuit breakers 4a and 4 of a plurality of distribution switchgears.
Measurement main bus board 5g consisting of: a plurality of distribution boards 7a, 7b which step down the voltage to a more desired voltage and house couple feeders 8 to 8b and a plurality of distribution circuit breakers 5a, 5b and 5c, fid. and distribution feeders 9a, 9b.

Power is supplied to each measuring instrument and controller via 9c and 9d.

Although the measurement mother board 5 as a power supply for measurement control has a small capacity due to its purpose, it receives power from the power distribution boards 1a and 1b.
It is desirable to keep output voltage fluctuations due to source voltage fluctuations and load fluctuations C2 within a constant value, and to keep the short-circuit current as low as possible in the event of a short-circuit failure on the load side.

[Problems with the background art] However, the above conditions are greatly affected by the impedance of the transformer 3 built into the main bus board 5 for measurement, and the distribution circuit breakers 6at, 6b, 6c, and ctd are used to keep the distribution current to a low level. (Secondly, it is possible to increase the impedance of the transformer 3. However, if the impedance of the transformer 3 is increased, the voltage fluctuation in response to the load fluctuation of the transformer 3 will increase, which will adversely affect the operation of the measurement control equipment and measurement accuracy.) Furthermore, during periodic inspections of the plant, etc. (the second is when the load status of the on-site power supply system changes, the power distribution board 1a is used accordingly).

The output voltage of 1b changes by Cm. When the voltage fluctuation rate is large, it often exceeds the specified range of the measurement controller, and the countermeasure in this case is to open the power receiving circuit breaker 2a or 2b each time, and put the measurement and control equipment into a temporary power outage state (after turning off the transformer). It was necessary to change the taps of the device 3, which required interruption of measurement and control and complicated work for switching Cm.

[Object of the Invention] The present invention has been made in view of the above, and provides a stable voltage measurement and control power supply in plants such as nuclear power plants, and facilitates protection coordination of circuit breakers that protect this equipment. The purpose is to provide a main bus board for measurement.

[Summary of the Invention] Measurement and control equipment for various plants such as nuclear power plants (main bus board for measurement that supplies dual power supplies has an automatic voltage regulator with high impedance built-in, so that the output voltage can be adjusted even when the power supply voltage and load fluctuate Cm) By maintaining Cm at a constant value, Cm, in the event of a circuit short-circuit failure (U), the fault current can be suppressed, the protection coordination and downsizing of various circuit breakers can be achieved, and the feeders of the two systems can be narrowly selected.

[Embodiments of the invention] An embodiment of the present invention will be described with reference to FIG.

Note that portions Cm that are the same as those in the prior art are given the same reference numerals, and detailed explanations will be omitted.

The measurement main bus board 10 of the present invention has two parts as a backup in case of failure.
It is comprised of power receiving circuit breakers 2m and 2b that receive AC power from either of the power distribution panels 1a, 1b or 1b of the system, an automatic voltage regulator 11, and a plurality of power distribution circuit breakers 4a and 4b. The built-in automatic voltage regulator 11 consists of, for example, a magnetic amplifier and a negative feedback circuit for this output voltage, and is a device that can always maintain the output voltage at a set value ζ- in response to fluctuations C2 in the applied voltage or load. , its impedance can be selected at the time of design.

The output of the main bus board 10 for measurement is the cable feeder 8a+8
b and distribution board 7 a e 7 b and distribution feeder 9a
, 9b, 9c.

A plurality of measuring instruments and control equipment (; supplied through 9d.

Note that the power receiving circuit breakers 2a and 2b are interlocked to prevent simultaneous power reception from both of the power distribution boards 1a and 1b of two systems with different main bus panels 10 for measurement.

The circuit is single-phase; for example, it receives 480V AC from the switchboard 1a, and receives 120V (50K) at the main bus board 10 for measurement.
When comparing the case where the voltage is stepped down and supplied to the distribution boards 7a and 7b, in the conventional main bus board 5ζ for measurement shown in FIG. 2, the secondary rated voltage of the transformer 3c is generally 480 V. , single-phase three-wire with secondary rated voltage of 240/120V.

I am using a transformer with a charging capacity of 50WVA, and the chain impedance of a normal capacity transformer is 5.7% (based on a 50kv person). Distribution feeder 9 is connected to this main bus board 5 for measurement.
When a short-circuit fault occurs, the short-circuit current flowing through the distribution breaker 6a, cable feeder 8m, and distribution breaker 4al is as shown in the following equation (1), assuming that the circuit impedance is only transformer 3. .

Considering the protection coordination between the distribution circuit breaker 4a and the distribution circuit breaker 6a for this short circuit current C2, it is necessary to select a distribution circuit breaker 4a that does not instantaneously interrupt this short circuit current (U is generally A breaker with a rated breaking current of 50OA or more is required, and a large one is required, and it is larger than the 8m cable feeder or the 9m cable feeder, which can withstand a short circuit current of 3.7"kA <-. It is also less economical because it requires a material with high and mechanical strength.In addition, the fluctuation rate of the output voltage with respect to a load change of 11JJl2 at this time is about 6%, and the fluctuation Cm of the power supply voltage changes in direct response to the output voltage. do.

In order to miniaturize the breaker and feeder in this conventional device, the short-circuit current must be kept low; Then that C
Therefore, the rate of voltage fluctuation becomes even greater, causing a decrease in the measurement accuracy of the measuring instruments and control equipment that are the load, and the inability to work properly. Of course, the tap of the transformer 3 must be changed every time the voltage fluctuates (it is also possible to adjust the voltage in two ways, but the degree of persistence and frequency are not yet determined, and it is necessary to create a power outage each time the voltage is changed). Therefore, it is impossible in practical terms of plant operation.

On the other hand, in the present invention, an automatic voltage regulator [1] shown in FIG.
1 is the primary rated voltage of 480 V, and the secondary rated voltage is 240 V.
/120V, single-phase 3ml, capacity 5OKVAte% (y heating length dance 15chi (5oWvλ pace), assuming the circuit impedance is only the automatic voltage regulator 11 as above, the following (2) It becomes like the expression.

This current value is about the same as that of the conventional example.

Therefore, when selecting a distribution breaker 4m in consideration of the protection coordination between the distribution breaker 4a and the distribution breaker 6a, the rated breaking current should be 200A or more (in other words, a small capacity breaker is sufficient. 8a and the distribution feeder 9a can also be made thinner and have lower mechanical strength, which is also advantageous in terms of economy.

Note that the output voltage to the distribution boards 7a and 7b is determined by the automatic voltage control action of the automatic voltage regulator 11 (C:) due to changes in the power supply voltage and load (since it can be maintained at about ±2-2-2) at all times, The accuracy of measuring instruments is improved, and the operation of control equipment is stabilized.Furthermore, there is no need to change taps when the voltage fluctuates, and of course there is no need for temporary power outages, so maintenance is unnecessary and reliability in plant operation is improved. Improves sex.

[Effects of the Invention] According to the present invention (2), the impedance of the automatic voltage regulator is increased and the impedance of the automatic voltage regulator is appropriately selected. becomes.

Furthermore, since short circuit current can be suppressed, there is an advantage that economical feeders can be used. Furthermore, the power source for the measurement and control equipment, which is the core of Nibrant operation, can be supplied with a stable power supply without voltage fluctuations or power outages, improving the accuracy of measurement and control, making maintenance unnecessary, and increasing the reliability of the plant. It has the effect of improving sex.

[Brief explanation of drawings]

FIG. 1 is a single line diagram of a main bus board for measurement according to the present invention, and FIG. 2 is a single line diagram of a conventional main bus board for measurement. 2a, 2b...Power receiving interrupter 4a, 4b...
Wiring breakers 5a, 5b, 5c, 5d - Distribution circuit breakers 7a, 7b - Distribution board ga, 8b... Cable feeder 9at 9b, 9c, 9d,..., Distribution feeder lO
...Measurement main bus board 11--Automatic voltage regulator agent Patent attorney Noriyuki Chika (and 1 other person) Figure 2

Claims (1)

[Claims] A main bus board for measurement, characterized in that, in a power supply facility for supplying control power to measurement control equipment, an automatic voltage regulator is provided as a voltage changing means.