Type CDG 11 Overcurrent and Earthfault Relay for AC series Tripping Type CDG 11 Overcurrent and Earthfault Relay for AC Series Tripping CDG 11 relay withdrawn from case Features General description Technical data Identical time/current characteristics on all taps. High torque, ensuring consistent timing even under adverse conditions. The CDG series trip relay is a slightly modified version of type CDG 11 relay which incorporates a secondary winding on the electromagnet of the CDG relay and an instantaneous unit. No overshoot. The operating coil can be supplied suitable for operation from 5.0 amps. or 1.0 amp. CT secondaries and the following standard setting ranges are available. Dust tight drawout case and tropicalised finish. Simple construction, easily accessible. Application Selective phase and earthfault protection in time graded system for AC machines, transformers, feeders etc. These relays are used where dc tripping supply is not available and trip the circuit breakers directly using the current from the current transformers. When the disc unit operates and closes its contacts, the instantaneous element connected across the secondary winding on the electromagnet operates, and opens its normally closed heavy duty contacts to allow the fault current to flow through the circuit breaker trip coil. The relay will safely control ac trip coil currents upto 150 amps. at 150 volts. When the trip current/ voltage exceeds these values, an external series resistor with or without a shunt choke is required. In all other respects, the ac series tripping relay is identical to the plain inverse time current relay type CDG 11. 50 - 200% adjustable in seven equal steps of 25% 20 - 80% adjustable in seven equal steps of 10% 10 - 40% adjustable in seven equal steps of 5%. Starting current 103 - 105% of current setting at TMS 1.0. Closing current Not more than 130% current setting. Resetting current The disc will completely reset at 90% or more of the current setting. Time settings Operating time 0-3.0 seconds or 0-1.3 seconds at 10 times the current setting. Time/current characteristics are identical to the IDMT characteristics or CDG 11. Resetting time With the time multiplier set at 1.0, the resetting time is 4 seconds and 9 seconds approximately for relays having an operating time of 1.3 seconds and 3.0 seconds respectively at ten times the current setting. Temperature error For an overload equal to ten times the current setting, the percentage timing errors at ambient temperatures of +45°C and 5°C are respectively 3.0 seconds relay : 3% and +4% 1.3 seconds relay : 4% and +4% Instantaneous unit and operation indicator Burdens 2VA at lowest tap 3.5VA at highest tap Thermal rating The maximum continuous current ratings for 60°C rise in coil temperature are as follows: Operating coil tap Frequency error A frequency variation of 2 Hz. gives timing errors of less than 8%. The time grading of a protective system would be unaffected by this small error since all relays would be similarly affected. Times current setting 1 4.5 2 3.7 3 3.2 4 2.7 5 2.6 6 2.4 7 2.2 The relay will withstand 20 times the maximum current setting for 3 seconds on any setting. Accuracy The relay conforms to error class index E 7.5 as per BS 142-1966 and 7.5 as per IS 3231-1965, at ten times reference current setting. The instantaneous unit of the relay is usually fitted with two pairs of hand reset heavy duty break contacts for connecting externally across the trip coils of the circuit breaker and 2 pairs of hand reset make contacts for alarm indication purpose. The instantaneous unit is fitted with an operation indicator which is hand reset by means of a push-rod protruding through the relay case. Contact ratings The two pairs of hand reset heavy duty contacts in parallel can break a maximum current of 150 amps. at 150 volts ac. The two additional pairs of hand reset standard make contacts when provided for alarm purposes can make and carry for 0.5 second 7500VA with maximum of 30 amps. and 660 volts, ac or dc. Insulation The relay will withstand 2.5 KV ac r.m.s. 50Hz for one second between all circuits and the case and between all circuits not intended to be connected together. It will also withstand 1.25 KV ac r.m.s. 50Hz for one second between mating contacts in open position. External and internal circuit connections Typical external and internal connections for type CDG 31 three phase overcurrent, alternatively combined overcurrent and earthfault protection, are shown in Figure 1. Case and finish Relays are supplied in drawout cases suitable for flush or projection mounting and are finished eggshell black and tropicalised. The drawout feature considerably simplifies maintenance and permits testing to be carried out easily and quickly. The case is fitted with switches which short circuit the associated current transformers on withdrawal of the relay unit from the case. A filter breather is fitted which equalises pressure inside and outside the case without admitting dust. Dimensions and weights Maximum overall dimensions Height Width Depth* mm mm mm Approximate gross weight Kg. Relay Case size CDG 11 series trip 1D Vert. 233 170 203 6.0 CDG 31 series trip 3D Hor. 233 454 203 15.5 3D Vert. 524 170 203 15.0 * Add 76 mm for maximum length of terminal studs, alternatively, 29 mm for terminal screws. The approximate gross weights given above are inclusive of cartons, mounting appendages and terminal details. The relays comply fully with the requirements of IS 3231-1965 and are suitable for use in normal tropical environments. Single pole relays are mounted in size 1D vertical case and triple pole relays are mounted in size 3D horizontal or vertical case, as required. Certified dimensional drawings of case outlines, panel cut-outs and mounting details are available on request. Information required with order 1. Type of relay (CDG 11 or 31) and system frequency. 2. Current setting range. 3. Characteristic (0 - 3.0 sec. or 0 - 1.3 sec. at 10 times current settings). 4. Operation indicator inscription, if required. 5. Case size. 6. Type of mounting - flush or projection. 7. Current transformer ratio and secondary winding resistance. 8. The knee-point voltage and the maximum voltage obtainable from the CT. 9. One way secondary lead resistance from CT to relay. 10. Nominal current rating of the trip coils. 11. The trip coil impedance with `plunger down and with `plunger up at the maximum and minimum tripping currents. 12. The operating voltage and the fault level of the primary circuit. Figure 1: Typical external and internal connections for CDG 31 ac series tripping relay ALSTOM Limited Pallavaram Works: 19/1, GST Road, Pallavaram, Chennai-600 043. India. Tel: 91-044-2368621 Fax: 91-044-2367276 Email: plw.applications@alstom.sprintrpg.eml.vsnl.net.in. © 1998 ALSTOM Limited Our policy is one of continuous development. Accordingly the design of our products may change at any time. Whilst every effort is made to produce up to date literature, this brochure should only be regarded as a guide and is intended for information purposes only. Its contents do not constitute an offer for sale or advice on the application of any product referred to in it. ALSTOM Limited cannot be held responsible for any reliance on any decision taken on its contents without specific advice. PR:011:0799:A Printed in India.
