PKV/M7: objective evaluating the state of high-voltage circuit breakers

20 may 2019

Most instruments for monitoring high-voltage circuit breakers available on the market today do not provide objective information about the technical condition of circuit breakers, because they do not take into account the features of checking either new or outdated equipment. Thus, the lack of objective information about the technical condition of the equipment leads to losses and waste of funds for its maintenance and repair.

Today, in the Russian market for monitoring high-voltage circuit breakers, there is a whole group of devices that differ from each other in the number of simultaneously controlled breaks, ways to adapt to various circuit breakers, temperature range, power supply voltage, the presence or absence of measurement methods, sensors used, additional functions, weight and, of course, price (see the table below).

WHAT YOU SHOULD BE GUIDED BY WHEN CHOOSING AN INSTRUMENT:

Question:	What parameters should be monitored for high-voltage circuit breakers?
Answer:	Time characteristics, speed, and stroke parameters. For SF6 circuit breakers, the time characteristics must be controlled simultaneously via 6 (12) channels, and for oil, electromagnetic, and vacuum circuit breakers — via 3 channels.
Question:	What are the requirements for the instrument?
Answer:	The instrument must obtain switching oscillograms and automatically calculated parameter tables based on them for all circuit breakers. In addition, for SF6 circuit breakers — speed measurement using sensors included in the breaker itself, as well as the calculation of the average speed for a certain section of the stroke. For oil and SF6 circuit breakers — installation of a linear and angular displacement sensor, as well as automatic conversion of the angular values of the stroke and speed to linear ones (for breakers where only angular rotation of the shaft can be monitored). Important is the requirement for an extended range of supply voltages for the device, since only a voltage of ~100V or =100V may be available at substations. Therefore, the device must work both from AC voltage ~85-265 V, and from DC voltage =100-375V. As you can see from the table below, the most suitable instruments for all switches is PKV/M7. Unlike competitors, it can perform the mentioned measurements and calculations automatically.
Question:	What sensors are used to measure speed and stroke?
Answer:	Digital sensors are more noise-resistant than potentiometric ones. This is inherent in the very principle of measurement. At substations of 500 kV and higher, potentiometric sensors are not able to operate under interference conditions. Each type of circuit breaker imposes its own specific requirements on the composition of the instrument. For oil and SF6 breakers this is the presence of linear and angular displacement sensors with attachment hardware. In addition, the sensor must measure movements up to 900 mm, since many oil circuit breakers, namely dead tank ones, have such a large stroke. According to the table, a set of necessary digital sensors and attachment hardware for switches is included in the scope of supply of PKV/M7, the linear displacement sensor of this device can measure the stroke up to 900 mm. The accuracy of measurements depends on the correct installation of the sensor, so the device must include a method for conducting measurements on breakers of any type.

Instrument type	PKV/M7	RME-500
Vacuum circuit breakers	+	+
SF6 circuit breakers	+	not all types
Oil circuit breakers	+	not all types
Discrete channels	4	5
Current measurement channels, A	up to 400	up to 50
Switch current, A	14	50
Sensor (L - linear, A - angular)	LA (digital)	LA (potentiometric)
T max of EO and EV control, s	1	2
Time measurement error, ms	±0.1	±0.1
Maximum stroke, mm	900	225
Operating temperature, °C	-20 ÷ +45	0 ÷ +55
Power supply voltage, V	~85-265, =100-375	~220
Measurement techniques	+	-
Weight, kg	7	8

Unlike competitors, PKV/M7 includes detailed measurement techniques for all types of circuit breakers.

PKV/M7 is necessary not only for companies that operate transformers, but also for organizations that are engaged in major repairs of old and installation of new equipment.