16
The registers of the overvoltage and under-
voltage relay contain useful information about
the behaviour of the power network during
normal service and in a fault situation.
On starting of the overvoltage stage the maxi-
mum value of the measured voltages is recorded
in register 1 as a multiple of the rated voltage.
Any new starting of the overvoltage stage erases
the old value from the register and a new value
is recorded. On operation of the overvoltage
stage the value gathering sequence is stopped
and the highest measured value during the start-
ing period is recorded.
Register 2 contains the maximum value of the
voltages measured after a relay reset as a multiple
of the rated voltage. The registered value is
updated any time when the value of the meas-
ured voltage exceeds the registered voltage value.
Register 2 must be erased by a command given
via the serial bus or by pressing the STEP and
RESET push-buttons simultaneously.
On starting of the undervoltage stage the mini-
mum value of the measured voltages is recorded
in register 3 as a multiple of the rated voltage.
Any new starting of the undervoltage stage
erases the old value from the register and a new
value is recorded. On operation of the under-
voltage stage the value gathering sequence is
stopped and the lowest measured value during
the starting period is recorded.
Register 4 contains the minimum value of the
voltages measured after a relay reset as a multiple
of the rated voltage. The registered value is
updated any time when the value of the meas-
ured voltage falls below the registered voltage
value. Register 4 must be erased by a command
given via the serial bus or by pressing the STEP
and RESET push-buttons simultaneously.
The number of startings, register 5 and 6, pro-
vides information on the occurance of
overvoltage and undervoltage in the network. It
must, however, be noted that when the start
time setting is 0.1 s, for instance, starting motors
can cause the undervoltage stage to start and the
value of register 6 to be updated. In the same
way the overvoltage stage may start on tempo-
rary overvoltages caused by, for instance, by a
voltage regulator.
Registers 7 and 8 show the duration of the latest
start situation of the stages, expressed in per cent
of the set operate time or of the calculated
operate time for the overvoltage stage. Any new
start erases the old value and a new value is
recorded. If the stage operates, the register value
will be 100.
The values of register 7 and 8 provide informa-
tion about the duration of the voltage variations
and how close to operation the overvoltage and
undervoltage stages have been. Furter informa-
tion is obtained about the function of the volt-
age regulator.
Register 2 and 4 provide information about the
limits of of fluctuation of the busbar voltage
during normal service.
Registers 1 and 3 as well as 7 and 8 facilitate the
post-fault analysis. These registers provide in-
formation about the voltage levels in a network
disturbance situation and how close to opera-
tion the overvoltage and undervoltage stages
have been.
Recorded data and
fault analysis
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