Diagnosis of HV circuit breakers state. The PKV/U3, a universal instrument in two modifications

19 january 2018

During mounting and adjustment of HV circuit breakers, switch gears (KRUE, KRU, KRUN, and KSO) and in the course of their subsequent maintenance their rated characteristics need to be checked, namely, time, speed, travel, current and voltage. Multiple tests are needed that are rather time-consuming (up to several days) and require a variety of instruments.

For this reason a universal instrument is recommended that allows precision control of all the required HV circuit breaker parameters in a short period of time. To meet those needs the SKB EP Company offers the PKV/U3 universal instrument for non-destructive control of Russian and foreign (ABB, SIEMENS и AREA) circuit breakers of all types (air, oil, SF6, vacuum ones) for all the voltage classes - from 10kV to 1150kV.

One of the PKV/U3 peculiarities is availability of two modifications of the instrument that differ in the number of displacement transducer channels (1 or 3) and the number of channels for resistive transducers (2 or 12): The PKV/U3.1 and PKV/U3.0, respectively.

Twelve test channels of resistive transducers integrated into the PKV/U3.0 allow control of all the types of circuit breakers, including VO-750, VO-1150, VNV-1150, whereas the PKV/U3.1 has only two channels, therefore, this model tests all the types of circuit breakers excluding the ones listed above.
The PKV/U3 is completed with transducers of angular (DP21) and linear (DP12) displacement for speed and travel characteristics control, but, unfortunately, users do not always use all the options of their combinations. Thus, for SF6 circuit breakers the DP12 transducer can be mounted on the operating rod connecting the mechanisms of circuit breaker poles, and the DP21 transducer can be mounted on the motor for compressing the drive springs. This combination allows measurement of current in the spring loading mechanism and control of a motor as a whole.
When measurements are performed using one displacement transducer, the travel parameters of each phase are measured by changing it from one phase to the other. Three CO (close-open) operations are needed in this case. But if three transducers are used at a time, this measurement can be done quicker as only one CO operation is needed.
Despite the fact that the PKV/U3 has been in manufacture for a long time and proved to be rather efficient, its capabilities have never been fully used. For example, amperage can be measured both by using a built-in switch of the instrument, and by current clamps (current value up to 600A; delivered upon order). The PKV/U3 users apply clamps mainly for measuring the solenoids of oil circuit breakers of MKP-110/220 and U-110/220 types, but they are being replaced by SF6 switch gears.
Thus, the need for measuring the high currents is replaced by the need for measuring the current of a motor for loading the drive springs. The PKV/U3 allows such tests and displays information on the actuation delay and on the state of the spring loading mechanism as a whole.
Availability of two channels for current measurement using current clips and a channel for measuring the voltage drop on the external instrument shunt allows simultaneous amperage control of three separate drives (for circuit breakers with separate drives). Two universal channels for voltage or resistance measurement allow connection of any transducers that are not included into the PKV/U3 kit. For example, contact displacement transducers for vacuum circuit breakers or additional current clips.

Thus, use of a universal PKV/U3 instrument reduces time of circuit breaker testing and allows early detection of faults by analyzing the digital data and displacement graphs, thus extending the service life of switching equipment.

"The PKV-U3 instrument is functional, easy to use, allows analysis of data in the tabular and graphic form, which considerably raises the labor efficiency during primary adjustment of equipment and its further tests".

A. Malkov, Chief Engineer of Electric Equipment Plant

"...Since the PKV/U3 design allows control of practically every rated parameter of a circuit breaker (proper close/open time, travel in contacts, delay in contacts closing/opening, squeeze, chatter, etc.), its use raises the quality of maintenance works. The function of measuring the consumed current by electric magnets windings allows detection of their concealed defects... Use of the PKV/U3 for non-destructive control of the circuit breaker nodes reduces the scope of maintenance works and allows early diagnosis of circuit breakers faults that need minor repair".

A. Burkeev, Engineer, Central Electric Networks. KEGOC Branch

"Use of the PKV/U3.1 instrument considerably reduces the time of HV circuit breakers check and raises the quality of works performed".

Yu. Tsyberny, Chief Engineer, Central Branch of Glavsetservis, Vologda PTOiR ENES