Basler Electric BE1-11t - Manual (Page 203)

9424200995 Rev H 191
Transformer Monitor (51TF)
The transformer monitor (51TF) element implements a through-fault counter which allows the user to
schedule wear-based maintenance instead of time-based maintenance.
Element logic connections are made on the BESTlogic
™Plus screen in BESTCOMSPlus® and element
operational settings are configured on the Transformer Monitor (51TF) settings screen in
BESTCOMSPlus. A summary of the logic inputs and outputs and operational settings appears at the end
of this chapter.
BESTCOMSPlus Navigation Path: Settings Explorer, Alarm Configuration, Transformer Monitor (51TF)
HMI Navigation Path: Settings Explorer, Alarm Configuration, Transformer Monitor 51TF
Element Operation
The 51TF element uses time characteristic curves to monitor the pickup count and report the through-
faults of a transformer.
Time Curve
The time current characteristic curve is the combination of up to three time curves each with their own
operating threshold and own curve constants. The curve being used is determined by current Threshold
Setting 1, Threshold Setting 2, and Threshold Setting 3. When the current is above Threshold Setting 1,
timing will be determined by TF
1
. If current increases above Threshold Setting 2 or 3, timing will be
determined by TF
2
or TF
3
respectively. Threshold Setting 3 has priority over Threshold Setting 2.
Threshold Setting 2 has priority over Threshold Setting 1.
TF
1
=
K1
(M − 1) N1
TF
2
=
K2
(M − 1) N2
TF
3
=
K3
(M − 1) N3
TF
X
= Time to Trip when M
≥ Threshold Setting x
M = Multiple of Transformer Base Current Setting
K, N = Constants for the particular curve
Pickup and Trip
When the measured current increases above the lowest of three threshold settings established by the
curve Threshold settings, the element Pickup output becomes true and the pickup counts are
incremented. When picked up, the element is timing towards the increment of the through-fault counter. In
BESTlogicPlus, the Pickup output can be connected to other logic elements to annunciate the condition
or control other elements in logic.
The through-fault counter will increment when the timing characteristic curve has been exceeded and the
Trip output will become true. In BESTlogicPlus, the Trip output can be connected to other logic elements
or a physical relay output to annunciate the condition and initiate corrective action.
CT Source
The CT Source setting configures the transformer monitor element to monitor CT circuit 1 or CT circuit 2.
CT circuit 1 terminals are designated D1 (IA1) through D8 (IG1) and CT circuit 2 terminals are designated
F1 (IA2) through F8 (IG2). For an illustration, refer to the
Terminals and Connectors chapter.
Alarm
A 51TF Through-Fault alarm indicates an alarm condition when the Through-Fault counts exceed the
Alarm Count setting. The alarm appears on the front-panel display, web page interface, and on the
BE1-11t Transformer Monitor (51TF)