ABB COV Series Памятка по эксплуатации - Страница 5

Просмотреть онлайн или скачать pdf Памятка по эксплуатации для Реле ABB COV Series. ABB COV Series 20 страниц. Voltage controlled overcurrent relay

Печатать страницу

COV Voltage Controlled Overcurrent Relay

current) and measure the operating time of the

relay. The operating times should equal those

of Table 1 plus or minus 5%.

For type COV-11 relay only, the 1.30 times tap

value operating time from the number 6 time

dial position is 54.8 ± 5% seconds and should

be checked first. It is important that the 1.30

times tap value current be maintained accu-

rately. The maintaining of this current accu-

rately is necessary because of the steepness

of the slope of the time-current characteristic

(Figure 8, page 17). A slight variation, ± 1%, in

the 1.3 times tap value current (including mea-

suring instrument deviation) will change the

timing tolerance to ± 10% and the effects of dif-

ferent taps can make the total variations

appear to be ± 15%.

6.2

VOLTAGE UNIT (V)

1) Contact Gap – The gap between the station-

ary contact and moving contact with the relay

de-energized

approximately .020".

2) Sensitivity – The contacts should close when

voltage is reduced to approximately 90 volts.

6.3

INDICATING CONTACTOR SWITCH (ICS)

Close the main relay contacts and pass sufficient dc

current through the trip circuit to close the contacts of

the ICS. This value of current should not be greater

than the particular ICS nameplate rating. The indica-

tor target should drop freely.

Repeat above except pass 85% of ICS nameplate

rating current. Contacts should not pickup and target

should not drop.

6.4

TELEPHONE RELAY (T)

The telephone relay has a dropout time of 250

milliseconds ± 50 milliseconds. It has a burden of

1.56 watts at 125 volts dc nominal. It should pickup

whenever the voltage unit contacts close.

7.0 ROUTINE MAINTENANCE

All relays should be inspected and checked once a

year or at other time intervals as dictated by experi-

ence to assure proper operation. Generally a visual

inspection should call attention to any noticeable

changes. A minimum suggested check on the relay

system is to close the contacts manually to assure

that the breaker trips and the target drops. Then

release the contacts and observe that the reset is

position

should

smooth and positive.

If an additional time check is desired, pass second-

ary current through the relay and check the time of

operation. It is preferable to make this at several

times pick-up current at an expected operating point

for the particular application. For the .05 to 2.5

amperes range CO-6 induction unit use the alterna-

tive test circuit in Figure 9 (page 18) as these relays

are affected by a distorted waveform. With this con-

nection the 25/5 amperes current transformers

should be worked well below the knee of the satura-

tion (i.e., use C 50 or better).

All contacts should be periodically cleaned. A contact

burnisher S#182A836H01 is recommended for this

purpose. The use of abrasive material for cleaning

contacts is not recommended, because of the danger

of embedding small particles in the face of the soft

silver and thus impairing the contact.

8.0 CALIBRATION

Use the following procedure for calibrating the relay if

the relay has been taken apart for repairs or the

adjustments disturbed. This procedure should not be

used until it is apparent that the relay is not in proper

working order (see "ACCEPTANCE TEST").

NOTE: A spring shield covers the reset spring of

the CO unit. Removing the spring shield

requires that the damping magnet be

removed first. The screw connection hold-

ing the lead to the moving contact should

be removed next. The second screw hold-

ing the moving contact assembly should

then be loosened, not removed. (Caution:

this screw terminates into a nut held cap-

tive beneath the molded block. If screw is

removed, difficulty will be experienced in

the re-assembly of the moving contact

assembly.) Slide the spring shield outward

and remove from relay. Tighten the screw

holding the moving contact assembly to

the molding block.

8.1

OVERCURRENT UNIT (CO)

A. Contact

1) By turning the time dial, move the moving

contacts until they deflect the stationary con-

tact to a position where the stationary contact

is resting against its backstop. The index

mark located on the movement frame should

coincide with the "0" mark on the time dial.

For double trip relays, the follow on the sta-

41-116.1C