9.41
Date Code 20080213 Instruction Manual SEL-351A Relay
Setting the Relay
Settings Explanations
The zero-sequence line impedance setting Z0MAG is automatically scaled by
the relay for use with neutral channel IN for directional control on low-
impedance grounded systems. See Z0F—Forward Directional Z0 Threshold
on page 4.46 and Z0R—Reverse Directional Z0 Threshold on page 4.46.
Line length setting LL is unitless and corresponds to the line impedance
settings. For example, if a particular line length is 15 miles, enter the line
impedance values (Ω secondary) and then enter the corresponding line length:
LL = 15.00 (miles)
If this length of line is measured in kilometers rather than miles, then enter:
LL = 24.14 (kilometers)
Delta-Connected PTs (PTCONN=DELTA)
Additional zero-sequence source impedance settings Z0SMAG (magnitude,
Ω secondary) and Z0SANG (angle, degrees) are required so that zero-
sequence voltage can be derived for fault locating.
Enable Settings
Refer to Instantaneous/Definite-Time Overcurrent Enable Settings on
page SET.2, Time-Overcurrent Enable Settings on page SET.2, Other Enable
Settings on page SET.2, and Breaker Monitor Settings (See Breaker Monitor
on page 8.2) on page SET.21.
The enable settings in Instantaneous/Definite-Time Overcurrent Enable
Settings on page SET.2, Time-Overcurrent Enable Settings on page SET.2, and
Other Enable Settings on page SET.2 (E50P–EDEM) control the settings that
follow, through SEL
OGIC Control Equation Variable Timers (See Figure 7.23
and Figure 7.24) on page SET.13. Enable setting EBMON in Breaker Monitor
Settings (See Breaker Monitor on page 8.2) on page SET.21 controls the
settings that immediately follow it. This helps limit the number of settings that
need to be made.
Each setting subgroup from Phase Inst./Def.-Time Overcurrent Elements (See
Figure 3.1, Figure 3.2, and Figure 3.3) on page SET.3 through SEL
OGIC
Control Equation Variable Timers (See Figure 7.23 and Figure 7.24) on
page SET.13 has a reference back to the controlling enable setting. For
example, the neutral-ground time-overcurrent element settings in Neutral-
Ground Time-Overcurrent Element—Channel IN (See Figure 3.18) on
page SET.7 (settings 51NP–51NRS) are controlled by enable setting E51N.
Other System
Parameters
Refer to Settings Group Change Delay (See Multiple Setting Groups on
page 7.18) on page SET.20.
The global settings NFREQ and PHROT allow you to configure the
SEL-351A to your specific system.
Set NFREQ equal to your nominal power system frequency, either 50 Hz
or 60 Hz.
Set PHROT equal to your power system phase rotation, either ABC or
ACB.
Set DATE_F to format the date displayed in relay reports and the front-
panel display. Set DATE_F to MDY to display dates in Month/Day/Year
format; set DATE_F to YMD to display dates in Year/Month/Day format.
NOTE: If global setting VSCONN =
3V0, settings Z0SMAG and Z0SANG
are not required, regardless of the
PTCONN setting.
Courtesy of NationalSwitchgear.com
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