1

GRID

PROTECTION

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 tropical-

ised finish.

Application

Overload and fault protection for ac gen-erators 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, incorpo-rated in the same case.

The relay has two operating characteris-tics, viz. an overload characteristic and a fault characteristic, determined by the op-eration of the instantaneous under-voltage unit monitoring the generator voltage. Un-der overload conditions, when the genera-tor voltage is usually normal, the instanta-neous 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 characteris-tic similar to the thermal withstand char-acteristics of the generator.

Under fault conditions, when the genera-tor terminal voltage falls, the resistor is shortcircuited and the torque on the disc is increased by 2.5 times so that the nomi-nal setting currents are 0.4 times those marked on the plug board, and the re-lay 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 under-voltage 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.

Voltage Controlled Overcurrent RelayCDV 22, 62

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.

2

CDV 62 Relay Drawn out from case

CDV 22, 62

Technical dataRatingsCurrent In:1A or 5AVoltage Vn

Relay Nominalrating V

Voltagesetting V

ResettingVoltage V

Type A 63.5 40 55

250 150 220

Type B 110 33 55

440 440 220

Setting rangesCurrent:50% - 200% in seven equal steps. This corresponds to a setting range of 20% - 80% for the fault characteristic.Time:

Condition Range at 4 timesthe current settings(s)

Overload 0-10

Fault 0-3

Starting current105 - 110% of current setting.

Closing current120 - 130% of current setting.

Resetting currentThe disc will completely reset at 90% or more of the current setting.

Resetting timeWith the time multiplier set at 1.0 the resetting time is 9 s when operating on fault characteristics.

OvershootOn 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.

BurdenCurrent coil:11.0VA approximately at the lowest tap.15.0VA approximately at the highest tap.

Voltage coil:6.0VA at nominal voltage.

Thermal ratingCurrent coil:The maximum current ratings for 60°C rise in coil temperature are as follows :

3

Tap (A) Continuousrating (A)

Maximum currentfor full operatingtime on overloadat TMS 1.0 (A)

1A relay 5A relay 1A relay 5A relay 1A relay 5A relay

0.5 2.5 0.9 4.5 14 70

0.75 3.75 1.11 5.6 13 65

1.0 5.0 1.28 6.4 12 60

1.25 6.25 1.35 6.75 11 55

1.5 7.5 1.56 7.8 10 50

1.75 8.75 1.68 8.4 9.4 47

2.0 10.0 1.76 8.8 8.6 43

The relay will withstand 16 times rated current for 3 seconds on any setting

Voltage coil:The continuous voltage ratings are as follows:

Relay Nominalrating V

Voltagesetting V

Type A 63.5 76

250 300

Type B 110 132

440 528

AccuracyThe relay conforms to error class index E 7.5 as per BS 142 and 7.5 as per IS 3231.

Frequency errorA 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 errorFor an overload equal to four times the current setting, the percentage timing errors at ambient temperatures of +45°Cand -5°C are respectively -3% and +4%.

Auxiliary units and operation indicatorsThe 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 op-eration 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 mini-mum 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.

Figure 2: Typical external and internal connections for type CDV 62B relay with shunt

reinforcing unit in size 3D double ended vertical case

CDV 22, 62

4

CDV 22, 62

InsulationThe relay meets the requirements of IS 3231IEC 2555 series C-2 kV for 1 minute.

CaseRelays 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 auto-matically 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 fit-ted 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 2500VA with maxima of 10A and 660V ac or dc

Two pairs of electrically separate self or hand re-set (provided on the aux-iliary unit)

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

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5

CDV 22, 62

Dimensions and weights

Relay Case size Maximum overall dimensions Approximategross weight kg.Height mm Width mm Depth * mm

CDV 22 1D 233 170 203 6.0

CDV 62 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 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 relay2. Current transformer secondary rating3. Nominal voltage rating4. Auxiliary voltage (for shunt reinforcing units)5. Auxiliary contacts - self or hand reset6. Case size

Figure 3 : Case and panel cut-out dimensions for case 3D vert drawout (all dimensions in mm)

6

GRID

Figure 5 : Case and panel cut-out dimensions for case 1D (all dimensions in mm)

Figure 4 : Case and panel cut-out dimensions for case 3D hor drawout (all dimensions in mm)

ALSTOM T&D INDIA LIMITEDPallavaram Works19/1, G.S.T. Road,Pallavaram, Chennai - 600 043Tel: 91-44-2264 8000Fax: 91-44-2264 0040

ALSTOM T&D Worldwide Contact Centre:http://www.alstom.com/contactcentre/Tel.: +44 (0) 1785 250 070

www.grid.alstom.com

CDV 22, 62

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