Basler BE1-CDS220, Instruction Manual

Page: 130 / 476

6-12 Reporting and Alarm Functions BE1-CDS220
of current is 150 milliamperes. In one-ampere relays, it is 30 milliamperes. If there is not enough current
present to run the algorithm, the message
I < 150 ma
(or 30 ma) appears in the appropriate alarm
column. Since all phase angles are referenced to A1, no current applied to A1 will cause the
I < 150
ma
(or 30 ma) message to appear for all phases.
The fifth part (MEASUREMENTS) displays the measured and calculated currents at the time of the
differential record trigger. The relay measures secondary current and develops the tap compensated
currents for use by the differential element. Primary current (
MEASURED I PRI
) is calculated simply as
the secondary current multiplied by the CT turns ratio. Secondary current (
MEASURED I SEC
) is the
current actually measured by the relay. Angle compensated current (
ANGLE COMPENSATED I
) is the
measured secondary current with phase compensation applied. Tap compensated current (
TAP COMP I
)
is the tap and phase compensated current actually used by the differential function. IOP is the operating
current. SLOPE RATIO is the ratio of
IOP
to the restraint current (maximum
TAP COMP I
). The slope
ratio is compared against the differential alarm setting. To generate a differential report and set the
differential alarm (alarm point number 3), two requirements must be met. One,
IOP
must be above the
alarm level setting times the minimum pickup setting. Two, the slope ratio must be above the alarm level
setting times the slope setting. For example, our settings are minimum pickup = 0.20, slope = 40%, and
differential alarm setting = 75%. Seventy-five percent of the minimum pickup is 0.75 times 0.2 = 0.15.
Operating current must be above 0.15 to satisfy requirement one. When a differential alarm setting of
75% and a slope ratio setting of 40, requirement two is satisfied when the slope ratio exceeds 30% (0.75
times 40 = 30%). See the following paragraphs on Setting Differential Current Monitoring Alarms and the
associated figure in this section for more information on slope ratios.
A new differential report will not be generated unless the slope ratio drops below the differential alarm
setting then increases above the setting. Alternatively, a record can be generated using the RA-
DIFF=TRIG ASCII command.
Example 1.
>RA-DIFF
CDS 220 DIFFERENTIAL CHECK RECORD
REPORT DATE : 11/10/98
REPORT TIME : 11:10:08.203
STATION ID : SIMULATED SUBST
RELAY ID : BANK-T1
USER1 ID : TEST1
USER2 ID : TEST1
RELAY ADDRESS : 0
ACTIVE GROUP : 0
87T SETTINGS CTR CT CON TX CON GROUNDED
CT CKT1 240 WYE DAC NO
CT CKT2 400 WYE WYE YES
MINPU 0.20 *TAP
SLOPE 25 %
ALARM 50 %
URO 6 *TAP
COMPENSATION Angle Tap
CT CKT1 WYE 3.12
CT CKT2 DAC 4.68
ALARMS PHASE A PHASE B PHASE C
DIFFERENTIAL: OK OK OK
POLARITY: OK OK OK
ANGLE COMP: OK OK OK
MISMATCH: OK OK OK
MEASUREMENTS PHASE A PHASE B PHASE C
MEASURED I PRI
CT CKT1: 209 @ 0 206 @ 240 206 @ 121
CT CKT2: 528 @ 211 516 @ 91 528 @ 332
MEASURED I SEC