SURGE PROTECTION CAPACITOR

SURGE PROTECTION CAPACITOR FOR HIGH VOLTAGE EQUIPMENTS: TECHNICAL DATA

Power apparatus is continuously subjected to abnormal voltages due to internal or external reasons. These may occur on account of lightening, switching operations, system faults and other abnormal conditions. Surge capacitors are capable of bringing down the steepness or slope of over voltage transients, that may appear accross transformer and other A.C. line connected equipments. Unless the transients are swamped effectively they may cause catastrophic failure of these devices. By reducing the slope of incoming surge conventional arresters fitted in conjunction with surge capacitors, the level gets truncated before operating across the insulation of a device. The surge capacitors must be designed to withstand and absorb damped or oscillatory line disturbances without affecting the mains frequency performance at the point of common coupling.

For the above purpose, normally 0.1 micro Farad, 0.25 micro Farad or 0.5 micro Farad capacitance is used. Typical Voltage rating is 3.3 kV, 6.6 kV, 11 kV or 33 kV. Other ratings may be supplied on request.

DESIGN & CONSTRUCTION

It is expected that a surge capacitor should never fail in service. The capacitor sections are of multilayer dielectric of P.P. Film and Foil design. In order to make units electrically tough and durable, large number of series sections are used with phase insulation many times greater than the system nominal voltage. To withstand higher transient currents, the windings are made with extended foil design. The dielectric is designed to cause very low loss at power freqencies. The containers are treated with two coats of red oxide primer and painted with two coats of synthetic enamel to resist moist atmosphere. They are rectangular and of heavy gauge steel welded with high quality arc welding. The surge capacitors are connected in Star with neutral grounded. Maximum cleareances are provided between the high voltage terminals.

RANGE OF PRODUCTS

The values given in the table are based on IS: 11548 /1986. However, other values also can be given on request. The RC network shall be given by providing the series resistor with the capacitor unit internally or externally. (Note: above 33 kV system voltages, the surge capacitors are manufactured as per customer’s specification).

TESTING

The capacitors manufactured will be subjected to Type and Routine Tests in the conventional way. as per IS:11548 or IEC specifications.

Table

System Voltage	3.3 kV	6.6 kV	11 kV	22 kV	33 kV

Capacitance in Mfd per Phase	0.1 to 0.5	0.1 to 0.5	0.1 to 0.5	0.1 to 0.5	0.1 to 0.5

Rated Voltage of Surge Capacitor per phase	6 kV	12 kV	18 kV	28 kV	40 kV

Impulse Voltage	60 kVP	75 kVP	100 kVP	140 kVP	190 kVP

High Voltage Capacitors || App P. F. Improvement Capacitors || Surge Capacitors || Water Cooled Capacitors
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