Basler BE1-CDS220, Instruction Manual

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BE1-CDS220 Reporting and Alarm Functions 6-11
Record IA IB IC IN IQ Time Date
1 595 599 599 0 0 06:29 01/01/99
2 595 599 599 0 0 06:14 01/01/99
3 595 599 599 0 0 05:59 01/01/99
4 594 598 598 0 0 05:44 01/01/99
5 594 598 598 0 0 05:29 01/01/99
6 593 597 597 0 0 05:14 01/01/99
7 593 597 597 0 0 04:59 01/01/99
8 592 596 596 0 0 04:44 01/01/99
9 591 595 595 0 0 04:29 01/01/99
10 590 594 594 0 0 04:14 01/01/99
11 589 593 593 0 0 03:59 01/01/99
12 588 591 591 0 0 03:44 01/01/99
13 586 590 590 0 0 03:29 01/01/99
14 584 588 588 0 0 03:14 01/01/99
15 582 586 586 0 0 02:59 01/01/99
16 580 583 583 0 0 02:44 01/01/99
17 577 580 580 0 0 02:29 01/01/99
18 573 577 577 0 0 02:14 01/01/99
19 569 573 573 0 0 01:59 01/01/99
20 565 568 568 0 0 01:44 01/01/99
21 559 563 563 0 0 01:29 01/01/99
22 553 557 557 0 0 01:14 01/01/99
23 546 549 549 0 0 00:59 01/01/99
24 537 541 541 0 0 00:44 01/01/99
25 528 531 531 0 0 00:29 01/01/99
26 516 519 519 0 0 00:14 01/01/99
DIFFERENTIAL CURRENT MONITORING FUNCTION
Differential current monitoring is a diagnostic function designed to aid in the installation and
commissioning of transformer banks. This function attempts to identify and prevent false trips due to
incorrect polarity, incorrect angle compensation, or mismatch.
During transformer commissioning, it would be particularly useful to analyze the system installation and
create a record of the settings and measured currents. The differential current monitoring function can
create a differential check record like the sample shown in the following paragraphs. These records are
also useful when comparing the present system characteristics to the characteristics at commissioning. A
differential record is generated automatically when the ASCII interface command RA-DIFF=TRIG (report
alarm-differential, trigger) is issued or when a differential alarm is set. When no alarms are active, you
must use the RA-DIFF=TRIG command to obtain a record of the actual operating conditions.
The following differential check record example was developed from a simulated substation and shows
that there are no problems in the installation or settings. The first part of the record is the date and time
the record was captured and the basic relay identification.
The second part is a record of the CT connections and 87 (differential) settings. These settings may be
entered using the S<g>-87 command. Refer to Section 3, Input and Output Functions, and Section 4,
Protection and Control, Differential Protection, for more information on entering settings that develop both
the second and third parts of the record. Also, refer to Section 3, Input and Output Functions, for
information on the CT polarity convention used in both the fourth and fifth parts of the record.
The third part is a record of the compensation factors. It is important to note that the angle compensation
cannot be entered manually. The angle compensation is calculated by the relay based on the CT and
transformer connections. (See Section 3, Input and Output Functions, Input Current, Setting Up the
Current Measurement Functions, for more information on automatically determining compensation.)
Additionally, the tap compensation setting may be entered manually or automatically calculated. (See
Section 4, Protection and Control, Differential Protection, for more information on auto-tap compensation.)
The fourth part of the record attempts to identify polarity and angle compensation errors by looking at the
phase angle differences of compared phases. The differential alarm is set whenever the minimum pickup
or the slope ratio exceeds the differential alarm, percent of trip setting. If the differential alarm is set and
neither the polarity alarm nor angle compensation alarm is set, a mismatch error is identified indicating
that the most likely cause of the alarm is incorrect tap settings. The differential check record needs a
specific amount of secondary current to properly measure phase angles. In 5-ampere relays, that amount