ABB REL650 Product Manual page 21

Line distance protection REL650 ANSI
Product version: 1.3
sequence source is weak or open, the forward source impedance
is strong and it is desired to detect forward ground faults.
Additionally, it is applied in applications on cables, where zero
sequence impedance depends on the fault current return paths,
but the cable negative sequence impedance is practically
constant.
The directional function is current and voltage polarized. The
function can be set to forward, reverse or non-directional
independently for each step. Both steps are provided with a
settable definite time delay.
DNSPTOC (46) protects against all unbalanced faults including
phase-to-phase faults. The minimum pickup current of the
function must be set to above the normal system unbalance level
in order to avoid inadvertent tripping.
6. Voltage protection
Two step undervoltage protection UV2PTUV (27)
Undervoltages can occur in the power system during faults or
abnormal conditions. Two step undervoltage protection
(UV2PTUV, 27) function can be used to open circuit breakers to
prepare for system restoration at power outages or as long-time
delayed back-up to primary protection.
UV2PTUV (27) has two voltage steps, where step 1 is settable as
inverse or definite time delayed. Step 2 is always definite time
delayed.
UV2PTUV (27) has a high reset ratio to allow settings close to
system service voltage.
Two step overvoltage protection OV2PTOV (59)
Overvoltages may occur in the power system during abnormal
conditions such as sudden power loss, tap changer regulating
failures, and open line ends on long lines.
Two step overvoltage protection (OV2PTOV, 59) function can be
used to detect open line ends, normally then combined with a
directional reactive over-power function to supervise the system
voltage. When triggered, the function will cause an alarm, switch
in reactors, or switch out capacitor banks.
OV2PTOV (59) has two voltage steps, where step 1 can be set as
inverse or definite time delayed. Step 2 is always definite time
delayed.
OV2PTOV (59) has a high reset ratio to allow settings close to
system service voltage.
Two step residual overvoltage protection ROV2PTOV (59N)
Residual voltages may occur in the power system during ground
faults.
ABB
Two step residual overvoltage protection ROV2PTOV (59N)
function calculates the residual voltage from the three-phase
voltage input transformers or measures it from a single voltage
input transformer fed from a broken delta or neutral point voltage
transformer.
ROV2PTOV (59N) has two voltage steps, where step 1 can be set
as inverse or definite time delayed. Step 2 is always definite time
delayed.
Loss of voltage check LOVPTUV (27)
Loss of voltage check LOVPTUV (27) is suitable for use in
networks with an automatic system restoration function.
LOVPTUV (27) issues a three-pole trip command to the circuit
breaker, if all three phase voltages fall below the set value for a
time longer than the set time and the circuit breaker remains
closed.
The operation of LOVPTUV (27) is supervised by the fuse failure
supervision SDDRFUF.
7. Frequency protection
Underfrequency protection SAPTUF (81)
Underfrequency occurs as a result of a lack of sufficient
generation in the network.
Underfrequency protection SAPTUF (81) measures frequency
with high accuracy, and is used for load shedding systems,
remedial action schemes, gas turbine startup and so on.
Separate definite time delays are provided for operate and
restore.
SAPTUF (81) is provided with undervoltage blocking.
Overfrequency protection SAPTOF (81)
Overfrequency protection function SAPTOF (81) is applicable in
all situations, where reliable detection of high fundamental power
system frequency is needed.
Overfrequency occurs because of sudden load drops or shunt
faults in the power network. Close to the generating plant,
generator governor problems can also cause over frequency.
SAPTOF (81) measures frequency with high accuracy, and is used
mainly for generation shedding and remedial action schemes. It is
also used as a frequency stage initiating load restoring. A definite
time delay is provided for operate.
SAPTOF (81) is provided with an undervoltage blocking.
Rate-of-change frequency protection SAPFRC (81)
The rate-of-change frequency protection function SAPFRC (81)
gives an early indication of a main disturbance in the system.
1MRK 506 337-BUS B
21