GE MFAC 14, Руководство пользователя, Страница: 10 / 25

Publication R6001 is a leaflet on the modular integrated drawout system of
protective relays.
Publication R6014 is a list of recommended suppliers for the pre-
insulated connectors.
Section 2. COMMISSIONING
2.1 Description of relay, calculation of setting and commissioning preliminaries
2.1.1 Description of MFAC 14/MFAC 34
This is a voltage operated relay having seven equally spaced settings of
15–185 volts, 25–175 volts, 25–375 volts or 100–400 volts which may be selected
by means of a plug bridge.
The relays may be used for any type of high impedance circulating
current protection.
2.1.2 List of abbreviations.
I
E
= Current transformer exciting current at relay setting voltage (referred to the
CT secondary current)
I
F
= Maximum value of primary through fault current for which protection must
remain stable.
I
FM
= Maximum value of primary fault current for internal fault.
I
P
= Primary current for operation of protection.
I
R
= Relay operating current.
I
SH
= Current in shunt resistor at relay setting V
R
.
N = Turns ratio of current transformer.
n = No. of current transformers in parallel with relay.
R
CT
= Secondary resistance of current transformer.
R
L
= Lead resistance between furthest current transformer and relay
connection point.
R
R
= Relay impedance.
R
SH
= Value of shunt resistor.
V
F
= The theoretical voltage which would be produced across the relay circuit
under internal fault condition.
V
F
= I
FM
(R
CT
+ 2R
L
+
R
R
) N
V
K
= Knee point voltage of current transformer.
V
P
= Peak voltage across relay circuit under maximum internal fault conditions.
V
S
= Minimum setting voltage. (calculated)
V
R
= Relay setting voltage.
2.1.3 Calculation of relay setting.
The minimum setting voltage to ensure stability is
V
S
≥
I F
(R
CT
+ 2R
L
)
N
The relay plug setting voltage V
R
must be set to the nearest tap above V
S
.
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