Schweitzer Engineering Laboratories SEL-321 - Miscellaneous Timers

Date Code 20011026 Applications 5-23
SEL-321/321-1 Instruction Manual
• Option 2 allows the trip contact to open if the trip condition has reset, the minimum trip
duration (TDURD) expires, and the 52A contact has changed state showing the breaker has
opened.
• Option 3 allows the trip contact to open if the trip condition has reset, the minimum trip
duration (TDURD) expires, the 52A contact has changed state showing the breaker has
opened, and the lowest set 50L, 50QF, or 50QR element is not picked up.
• Option 4 allows the trip contact to open if the trip condition has reset, the minimum trip
duration (TDURD) expires, and the input assigned to EXTUL is asserted.
For our example, Option 3 is used.
EPOLD = N
NN
N
ESPT = N
NN
N
ESPO = N
NN
N
3POD = 1.50
1.501.50
1.50
ESTUB = Y
YY
Y
50MFD = 20.00
20.0020.00
20.00
TULO = 3
33
3
- Relay Elements and Other Settings Affected
50MF element.
Miscellaneous Timers
The SEL-321 Relay provides dedicated timers for additional relay element variables so that you
may create your own scheme logic. The minimum trip duration, trip during open pole, and
instantaneous trip time declaration timers are also included in these settings.
The minimum Trip Duration timer (TDURD) setting determines the minimum length of time the
TPA, TPB, TPC, and 3PT relay element asserts. These relay elements are used to control a
designated trip contact. The trip output contacts close for the greater of the TDURD time or the
duration of the trip condition. A typical setting for this timer is 150 msec or nine cycles.
The trip during Pole Open Time Delay (TOPD) is not used in the three-pole tripping logic and is
set to zero.
Timers are provided for the X, Y, and Z SEL
OGIC control equation variables. This allows you to
invent your own protection or control schemes using the internal relay elements.
The Instantaneous Trip Time (ITT) declaration delay qualifies a maximum time for instantaneous
targeting. This is determined by the time an element set in the trip equation is picked up before
the trip output is asserted. If the element is picked up for less than the ITT time before the trip
output, it is declared an instantaneous trip for targeting purposes. The relay also declares an
instantaneous target if a trip occurs and no other targeting conditions are true.