BECKWITH ELECTRIC Syncrocloser M-3410A, Instruction Book

Page: 91 / 225

M-3410A Instruction Book
3–20
32 Directional Power, 3-Phase or 1-Phase
Directional Power protection (32) is available in
either the Reverse Overpower, Reverse Underpower,
Forward Overpower or Forward Underpower
configuration presented in Figure 3-26. A power
import and export convention that considers
Dispersed Generation (DG), Utility and the M-3410A
perspectives is also included. The directional power
function provides two power elements, each with a
direction setting, magnitude setting and time delay,
and configurable as an underpower or overpower
element.
Generator Protection:
The directional power
function may provide both generator motoring and
overload protection. Forward power is defined as
power exported from the generator, and reverse
power is defined as power absorbed by the generator
(see Figure 2-8 and 2-10).
Two power elements are provided, each with a
magnitude setting and time delay. The setting range
is from –3.00 PU to 3.00 PU where 1 PU is equal to
the generator MVA rating. Normalized PU power
flow measurements are based on the Nominal
Voltage and Nominal Current setting, as shown in
Section 3.1, Relay Configuration, Relay Setup.
Interconnection Protection: Power protection may
be useful as a means of fault backfeed protection
and loss of utility supply, depending upon the size
of the DG, the DG’s load, the feeder load, and utility
import/export restrictions. Forward power is defined
as power exported from a DG to a Utility, and
reverse power is defined as power imported by a
DG from a Utility (see Figures 2-9 and 2-11).
The Directional Power function includes a three-
phase operation that, when selected, uses total
three-phase power measurements. When Three-
Phase Detect is disabled, the M-3410A detects the
power in each phase, and operates if the power in
any one phase exceeds the setpoint. Individual
single phase power protection is available only with
line-to-ground connected VT’s.
Two power elements are provided, each with a
magnitude setting and time delay. The setting range
is from –3.00 PU to 3.00 PU. The choice of the
base PU is typically taken from the MVA rating of
the interconnection transformer, the DG’s aggregate
generating capacity or some other value agreed
upon by the DG and the Utility. Normalized PU
power flow measurements are based on the Nominal
Voltage and Nominal Current setting, as shown in
Section 3.1, Relay Configuration, Relay Setup.
If the DG is allowed to supply power to the Utility
(export), the forward overpower function can be
used to limit the amount of power flow into the
Utility. In peak shaving applications, where no export
of power form DG to the utility should ever occur,
the reverse underpower function can be used to
ensure that the DG is importing a minimal amount
of power from the Utility, therefore providing a
supplemental means of loss of parallel operation
protection.
Configuration Process
The directional power elements are individually
configured as follows:
1. Input the desired pick up value, positive
(forward) or negative (reverse).
a. Positive pick up value – Places the
pick up point in the forward power
area of the element, creating a
forward power element.
b. Negative pick up value – Places the
pick up point in the reverse power
area of the element, creating a
reverse power element.
2. Select either Overpower or Underpower
application:
Overpower Mode
a. Reverse Overpower – An increase
in reverse power flow that exceeds
the pick up value will cause a trip.
b. Forward Overpower – An increase
in forward power flow that exceeds
the pick up value will cause a trip.
Underpower Mode
a. Reverse Underpower Mode – A
decrease in reverse power flow that
is below the pick up value will cause
a trip.
b. Forward Underpower Mode – A
decrease in forward power flow that
is below the pick up value will cause
a trip.
3. If configured for line-to-gnd VT
connections, select either three-phase
or individual single-phase detection.
▲ ▲ ▲ ▲ ▲
CAUTION: Proper CT polarity is important in
defining the direction of power flow. Refer to Figures
2-9 and 2-10 for proper connections.
32 # 1 & #2 Pickup – If the pickup is set positive,
the element is a forward power element. If the
pickup is set negative, the element is a reverse
power element.