CDV 22, 62. Voltage Controlled Overcurrent Relay GRID PROTECTION

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1 PROTECTION CDV 22, 62 Voltage Controlled Overcurrent Relay CDV22 relay is used for overload and fault protection for ac generators when the sustained short circuit current is less than the full load current. The presence of a fault is detected by an under voltage element and the relay setting is adjusted accordingly. Features Two time-current characteristic curves in one unit to provide overload and fault protection. Identical time-current characteristics on all taps. High torque, ensuring consistent timing even under adverse conditions. Very low overshoot. Simple construction, easily accessible. Dust-tight drawout case and tropicalised finish. Application Overload and fault protection for ac generators when the sustained short circuit current is less than the full load current. Description CDV is a non-directional heavily damped induction disc relay similar to relay type CDG 11 but having an electromagnet fitted with shading coils instead of solid copper shading rings. The circuit of shading coils is completed through a resistor which is shorted by a normally closed contact of the instantaneous undervoltage unit, incorporated in the same case. The relay has two operating characteristics, viz. an overload characteristic and a fault characteristic, determined by the operation of the instantaneous under-voltage unit monitoring the generator voltage. Under overload conditions, when the generator voltage is usually normal, the instantaneous under-voltage unit is energised and the short across the resistor in the shading coil circuit is removed. The relay operates on a long I.D.M.T. or overload characteristic similar to the thermal withstand characteristics of the generator. Under fault conditions, when the generator terminal voltage falls, the resistor is shortcircuited and the torque on the disc is increased by 2.5 times so that the nominal setting currents are 0.4 times those marked on the plug board, and the relay operates in accordance with the fault characteristic. The relay characteristics are shown in Figure 1. Type CDV relay is available in two versions. Type A relay changes its characteristic at 60% normal voltage and is used when the generator neutral is solidly earthed. The undervoltage unit is connected between phase and neutral and the relay operates for both phase and earth faults. Type B relay changes its characteristic at 30% normal voltage and is used when the alternator neutral is earthed via a resistor or a distribution transformer. The undervoltage unit is connected between two phases and the relay operates for phase faults only. Type CDV 22 is a single pole relay and CDV 62 is a three pole version of CDV 22. Typical external and internal connections for relay CDV 62B with shunt reinforcing unit are shown in Figure 2. Customer Benefits Simple construction Easy accessibility. Drawout case. GRID 1

2 Technical data Ratings Current I n : 1A or 5A Voltage V n Relay Nominal rating V Voltage setting V Resetting Voltage V Type A Type B Setting ranges Current: 50% - 200% in seven equal steps. This corresponds to a setting range of 20% - 80% for the fault characteristic. Time: Condition Range at 4 times the current settings(s) Overload 0-10 Fault 0-3 CDV 62 Relay Drawn out from case Overshoot On removal of a current equal to 8 times the current setting, the overshoot time is less than 0.04 s when operating on fault characteristic. Burden Current coil: 11.0VA approximately at the lowest tap. 15.0VA approximately at the highest tap. Starting current % of current setting. Closing current % of current setting. Resetting current The disc will completely reset at 90% or more of the current setting. Voltage coil: 6.0VA at nominal voltage. Thermal rating Current coil: The maximum current ratings for 60 C rise in coil temperature are as follows : Resetting time With the time multiplier set at 1.0 the resetting time is 9 s when operating on fault characteristics. 2

3 Tap (A) Continuous rating (A) Maximum current for full operating time on overload at TMS 1.0 (A) 1A relay 5A relay 1A relay 5A relay 1A relay 5A relay The relay will withstand 16 times rated current for 3 seconds on any setting Voltage coil: The continuous voltage ratings are as follows: Relay Nominal rating V Voltage setting V Type A Type B Accuracy The relay conforms to error class index E 7.5 as per BS 142 and 7.5 as per IS 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. Temperature error For an overload equal to four times the current setting, the percentage timing errors at ambient temperatures of +45 C and -5 C are respectively -3% and +4%. Figure 2: Typical external and internal connections for type CDV 62B relay with shunt reinforcing unit in size 3D double ended vertical case Auxiliary units and operation indicators The relay has an auxiliary unit fitted with two pairs of self, hand, or combined self and hand reset contacts, arranged to reinforce the disc contact. It is also fitted with an operation indicator which can be hand reset by means of a push-rod protruding through the relay case.auxiliary units are shunt connected (voltage operated) or series connected (current operated). The series connected auxiliary unit is put in series with a circuit breaker trip coil or tripping relay. It has two current taps which are marked with the minimum current required for operation and are selected by screw connections on the unit Coil rating: Voltage operated (shunt) auxiliary units 30, 110 or 220V dc with a nominal burden of 3W. Current operated (series) auxiliary units 0.2/2.0A (two taps) minimum operating current. The current rating of the auxiliary unit is 22A for 0.5 s at 0.2A tap and 92A for 0.5 s at 2.0A tap. Other coil ratings are available on request. 3

4 Insulation The relay meets the requirements of IS 3231IEC 2555 series C-2 kv for 1 minute. Case Relays are supplied in drawout cases suitable for flush mounting and are finished eggshell black and tropicalised. The drawout feature considerably simplifies maintenance and permits testing to be carried out easily and quickly. A cradle-mounted isolating switch is provided which automatically isolates the trip circuit when the cradle assembly is withdrawn from the case for maintenance. This prevents any inadvertent tripping of the circuit breaker. The case is fitted with switches which prevent opencircuiting of the current transformer circuits 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.the triple pole relays are mounted in size 3D horizontal or vertical case, as required. Contact ratings Type of contact Make and carry for 0.5 second Single disc Two pairs of electrically separate self or hand reset (provided on the auxiliary unit) 2500VA with maxima of 10A and 660V ac or dc 7500VA with maxima of t 30A and 660V ac or dc Figure 2: Typical external and internal connections for type CDV 62B relay with shunt reinforcing unit in size 3D double ended vertical case 4

5 Dimensions and weights Relay Case size Maximum overall dimensions Approximate gross weight kg. Height mm Width mm Depth * mm CDV 22 1D CDV 62 3D Hor D Vert * Add 76 mm for maximum length of terminal studs, alternatively, 29 mm for terminal screws. The approximate gross weights given above are inclusive of carton mounting appendages and terminal details. The relays comply fully with the requirements of IS 3231 and are suitable for use in normaltropical environments. Information required with order 1. Type of relay 2. Current transformer secondary rating 3. Nominal voltage rating 4. Auxiliary voltage (for shunt reinforcing units) 5. Auxiliary contacts - self or hand reset 6. Case size Figure 3 : Case and panel cut-out dimensions for case 3D vert drawout (all dimensions in mm) 5

6 ALSTOM T&D INDIA LIMITED Pallavaram Works 19/1, G.S.T. Road, Pallavaram, Chennai Tel: Fax: ALSTOM T&D Worldwide Contact Centre: Tel.: +44 (0) Figure 4 : Case and panel cut-out dimensions for case 3D hor drawout (all dimensions in mm) Figure 5 : Case and panel cut-out dimensions for case 1D (all dimensions in mm) GRID Alstom logo and any alternative version thereof are trademarks and service marks of Alstom. The other names mentioned, registered or not, are the property of their respective companies. The technical and other data contained in the document are provided for information only. Neither ALSTOM, its officers nor employees accept responsibility for or should be taken as making any representation or warranty (whether express or implied) as to the accuracy or completeness of such data or the achievements of any projected performance criteria where these are indicated. No liability is accepted for any reliance placed upon the information contained in this brochure. Alstom reserves the right to revise or change these data at any time without further notice. 6