Operation: CP1SD/T/L Version
76
CENTRON® Polyphase Meter Technical Reference Guide
By using the equations above and substituting in the voltages for the upper and lower limits,
one can also see why the diagnostic check has failed. For Diagnostic #2 to pass, the
following equations must be satisfied:
3
.
107
279.1
and
131.1
1
.
279
2
.
119
%)
10
1
(
279.1
and
119.2
%)
10
1
(
1
.
279
3
.
107
274.5
and
31.1
1
4
.
275
2
.
119
%)
10
1
(
275.4
and
119.2
%)
10
1
(
4
.
275
>
<
•
−
>
•
+
<
>
<
•
−
>
•
+
<
and
One can see in the above equations that 275.4 and 279.1 are not less than 131.1. Further
investigation can begin on the circuit to determine the cause of the problem.
SiteScan Diagnostic #3
The purpose of this diagnostic is to verify that each individual phase current maintains an
acceptable current level with respect to the others. This diagnostic check may indicate one
or more of the following problems:
Current diversion
Open or shorted current transformer circuit
Internal meter measurement malfunction
During the test, if one or more currents fall below the user defined “low current threshold”,
and at least one current is above this level, then a diagnostic error is triggered.
Inactive Phase Current Check
Diagnostic #3 checks every five seconds to verify that the meter is receiving a configured
current level for each individual phase. If the meter fails three consecutive checks, the
Diagnostic #3 check will trigger.
Once every five seconds, all phase currents are checked against a user-defined “low current
value” to verify that the current value is above this value. If one or more currents fall below
the low current value,
and
at least one current remains above this value for 3 consecutive
checks, the CENTRON Polyphase meter will trigger the error. The error will not be
triggered if all the currents fall below or above the user-defined value.
The starting current of:
transformer rated meters, CL 20, is 5 mA.
self-contained meters, CL 200, is 50 mA.
the CL320 version is 80 mA.
Therefore, a selected “low current value” of 100 mA would require at least one phase above
and below the starting current in order to activate the diagnostic.
