KCEG142 データシートの表示（PDF） - Unspecified

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KCEG142

Overcurrent Protection

Unspecified 

Circuit breaker failure and back-trip

This protection feature allows the relay

to trip the upstream circuit breaker

when a local breaker failure condition

is detected and can be energised both

from operation of the relay or an

external trip. Figure 3 shows a typical

back-trip method for a fault on Feeder

1 that should be cleared by Relay 2

and circuit breaker B (CB-B). If CB-B

fails to clear the fault, it will be

cleared by the back-trip contact of

Relay 2 tripping CB-A.

faults, an economical form of busbar

protection can be applied to a system.

This can be used where dedicated

busbar protection can not be justified.

Rectifier protection

A special inverse time curve provides

protection for silicon rectifiers. Where

used with the thermal overload,

instantaneous short circuit and

restricted earth fault protection, both

the transformer and rectifier can be

fully protected.

Undervoltage protection (KCEG)

A separate characteristic can be set to

provide an output for undervoltages

which are phase-phase, phase-neutral,

three phase or single phase.

An independently set timer, tV< is

used with this function which can

allow a voltage controlled overcurrent

feature to be created by switching

between different current settings in

the two groups. The undervoltage

element can be blocked when the

circuit breaker is open.

Underfrequency

A delayed underfrequency element is

available which can be used to

initiate direct load shed tripping.

Broken conductor detection

The relay can provide a broken

conductor alarm when it detects load

current in only two out of three

conductors.

Circuit breaker maintenance data

An alarm is provided to indicate the

need for circuit breaker maintenance

based upon the number of circuit

breaker operations or upon the

summated contact breaking duty.

The circuit breaker trip time is stored

in the fault records.

Busbar protection

Protection of busbars can also be

achieved by using the start and

blocking contacts of the K relays.

If in Figure 3, relay 1 has a standard

IDMT characteristic for I>, but a fast

acting I>> element (time delay of

typically 50ms) which is blocked by

the downstream relays for feeder

Incomer

CB-A

Relay 1

Back trip

CB-B

Relay 2

CB-C

Relay 3

CB-D

Relay 4

Feeder 1

Feeder 2

Figure 3: Back trip fault clearance

Feeder 3

Configuration

Logic

The configuration of the relay, to meet

the required applications, is

accomplished in software. Setting

logic function links, together with the

assignment of inputs and outputs,

define the way that the relay will

operate. This allows:

q Selection of features

q Implementation of user defined

logic using auxiliary timers

q Control of the integral disturbance

and event recorder

These may be defined by the user via

the relay front panel function keys, or

remotely by a PC via the

communications system.

Alternative setting group

Two setting groups allow the user to

assign settings for different operating

conditions. Several methods of

selecting the alternative setting group

are provided.

Ancillary Functions

Measurements

The measurement values provided by

the relay can be accessed by an

integral back-lit liquid crystal display

or via the serial port eliminating the

need for additional instrumentation to

be mounted on the panel. The

measurements can be displayed in

either primary or secondary values as

selected by the user.

The following quantities are provided

as standard:

q phase current

q neutral current

q frequency

q thermal ammeter

q peak demand ammeter

Additional values are provided by the

KCEG, as follows:

q phase voltage

q line voltage

q zero sequence voltage

q watts (single phase and three

phase)

q VArs (single phase and three

phase)

q volt amps

q power factor

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