Coupling Capacitors and Voltage Dividers

As the network of high-voltage electricity transmission lines develops, its length increases and equipment is outfitted with automation, there is a need for reliable dispatching and administrative and business communication between individual points, transmission of telemetering signals, emergency shutdown of switches, relay protection and other data. Usually such a connection is carried out directly by high-voltage electric transmission lines.
One of the elements of such communication equipment are capacitors, which separate communication equipment from high voltage of 50 Hz frequency, passing high frequency signals through communication channels. On the basis of the same capacitors, power take-off devices are made at a frequency of 50 Hz directly from electricity transmission lines to power/supply the measuring equipment, as well as measuring devices (dividers, voltage transformers) to measure the voltage of electricity transmission lines.

Depending on application scope, rated voltage, type of external insulation, the following types of coupling capacitors are manufactured:

  • capacitors in porcelain reinforced and non-reinforced cases;
  • in composite cases;
  • in metal cases;
  • capacitors of explosion-proof performance;
  • of amplified performance;
  • of suspended performance;
  • as well as capacitive voltage dividers.

For lines with voltage 150 ÷ 500 kV, columns of two or three capacitors are used as a rule.

Coupling capacitors of explosion-proof performance are designed to replace common coupling capacitors on electricity transmission lines. Explosion proofness is ensured by a specially designed and tested explosion protection unit. As a result the capacitors have an increased resistance to the effects of internal short circuit energies and prevent explosions that are dangerous to the surrounding equipment and personnel. Coupling capacitors can be manufactured both in porcelain and in composite cases with silicone ribs.
Coupling capacitors of explosion-proof performance are successfully passed high-voltage tests as part of qualification tests on the base of Testing Center of NTC FGC UES branch – SibNIIE, in the city of Novosibirsk.
To test an operation of explosion protection assembly, full-scale tests were carried out. The tests were conducted on the basis of Shatura branch of High Temperatures Institute of Russian Academy of Sciences. For these tests, a special methodology was developed coordinated with FGC UES. The tests were fulfilled with the help of arcless source of impulse pressure.

As for today more than 300 sets of coupling capacitors of explosion-proof performance have been sold, including 30 columns of coupling capacitors of type KCA-500 for “Yelabuga” Substation.
Coupling capacitors of explosion-proof performance have the following advantages:
• provide increase of reliability and safe operation of equipment in case of technological violations;
• provide increased safety for personnel and maintenance services;
• provide reliable power supply to consumers;
• ecologically safe;
 • and also help to reduce the material consequences at technological violations.

Also Ust-Kamenogorsk Capacitor Plant manufactures amplified coupling capacitors with the possibility to install a high-frequency trap. As a rule, the trap is suspended on portal supports or spider-beams. However, in the typical project of 110 kV substations, there are no portal supports, and the trap is installed directly on the coupling capacitor. 110 kV old design capacitors had large dimensions and, consequently, bigger mechanical strength compared to modern ones, therefore there were no any problems with installation of trap onto the capacitor.

As capacitor technology develops, new materials appear, the dimensions of capacitors have decreased. Thus, UKCP developed a coupling capacitor of amplified performance with enhanced mechanical characteristics. This capacitor allows the installation of trap weighing up to 310 kg. trap fastening is carried out with the help of a standard fastening unit, however, in agreement with the customer it is possible to develop fastening unit according to individual requirements.
“UKCP”, Ltd. also supplies equipment for processing of high-frequency signal, high-frequency traps of various types, connection filters, equipment for communication channels and telemechanics.

Ust-Kamenogorsk Capacitor Plant has developed a suspended coupling capacitor for power take-off device. The power take-off device is designed to take off active electrical power up to 1000 W inclusive from industrial frequency AC networks with a rated voltage 110 kV.
This device consists of suspending or supporting high-voltage transducer, suspended on the support of electricity transmission line or mounted on a support structure and output cable.
It can also be equipped with an uninterruptible power cabinet. High-voltage transducer is a combined step-down transformer 110 / 0.22 kV with power from 300 up to 1000 W. Its distinctive feature is the ability to work in any spatial position, small overall dimensions and weight.
The power take-off device is an analogue to a step-down transformer regarding its electrical parameters and can be used to power telemetry devices and relay protection, communication equipment, commercial metering stations and other similar equipment.