Relay Element Settings 2-13
SEL-300G Instruction Manual Date Code 20020206
Zone 2 Phase Distance Reach (OFF, 0.1 to 100.0 ohms) Z2R = 8.0
Zone 2 Phase Distance Offset (0.0 to 10.0 ohms) Z2O = 0.0
Set Z2R to define the forward (toward the system) phase distance reach, defined in
secondary ohms. Because the relay includes a load encroachment function for distance
element security under heavy load, load impedance is not a concern when selecting the
Z2R reach setting. Setting Z2R = OFF disables the element and causes the relay to
hide the balance of the settings associated with Zone 2.
The Z2O setting defines the Zone 2 element offset. When an SEL-300G0 or
SEL-300G2 Relay is applied with current transformers as shown in Figure 5.16 or
Figure 5.17, you may wish to apply a positive offset equal to the generator impedance
as backup generator phase-to-phase fault protection.
Zone 2 Maximum Torque Angle (90 to 45 degrees) MTA2 = 88
Set MTA2 equal to the angle of the transformer plus system impedance defined by the
Zone 2 reach setting. The relay places the distance element maximum reach along a
line at the angle defined by the MTA2 setting.
Zone 2 Transformer Compensation Angle (0, -30, +30 degrees) Z2CMP = 0
Use the Z2CMP setting to compensate the phase distance element for the presence of a
delta-wye generator step-up transformer between the generator and system. When the
element is not set to reach through the step-up transformer, set Z2CMP = 0. When the
element is set to respond to phase faults on the high side of a delta-wye transformer,
and the system phase-neutral voltage phase angle leads the generator phase-to-neutral
voltage phase angle by 30°, set Z2CMP = -30°. When the system phase-to-neutral
voltage phase angle lags the generator phase-neutral voltage phase angle by 30°, set
Z2CMP = 30°.
Zone 2 Phase Distance Time Delay (0.00 to 400.00 s) Z2D = 0.00
The Z2D setting defines the Zone 2 element definite-time delay.
Minimum Power Factor (OFF, 0.98 to 0.50) MPF = 0.80
Maximum Generator Load (0.5 to 3.0 per unit) MXLD = 1.2
The MPF and MXLD settings define the operation of a simple load encroachment
function that increases the security of the phase distance elements under heavy load. If
load encroachment security is desired, set MPF to the minimum rated generator power
factor under maximum load conditions. Set the maximum emergency generator power
output in per unit of the generator rating. If load encroachment security is not desired,
set MPF = OFF to disable the function.
21P Element Torque Control (SEL
OGIC Control Equation) 21PTC = !3PO
The phase distance elements are enabled when the result of 21PTC equals logical 1.
The elements are blocked when the 21PTC SEL
OGIC Control Equation result equals
logical 0. Typically, the 21PTC SEL
OGIC Control Equation should be set so the
elements are enabled when the generator main circuit breaker is closed (!3PO). Other
supervisory conditions may be added if your application requires.
Note: Loss-of-potential (60LOP) supervision is built into the element logic so it does
not need to be added to the 21PTC SEL
OGIC Control Equation setting.
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