Voltage Based Protection Functions; Signal Flow Of The Voltage Based Protection And Monitoring Functions; Total Harmonic Distortion - ABB UMC100.3 Manual

C O N F I G U R I N G T H E M OTO R P R OT E C T I O N F U N C T I O N S

Voltage based Protection Functions

The following block diagram provides an overview of the signal flow related to voltage supervision and protection. The different
voltage protection functions are usually always active (also if the motor is in stop mode). There are two exceptions a) if the UMC is
in test position and b) if a voltage Dip was detected.
Disable
Voltage dip
Max
U
L1L2
U
L2L3
Min
U
L3L1
Imbalance
Calculation
Phase
loss
detection
THD MAX
Calculation
delay = dip duration or dip autorestart delay (the longer time is used for the delay)
1)
—

Signal flow of the voltage based protection and monitoring functions

Imbalance
An imbalance can appear because of different reasons. For example because of a network imbalance or because of high contact re-
sistances in the wiring of a phase. Even small voltage imbalances causes high current imbalances. The imbalance value is calculated
as follows (max. deviation (U12,U23,U31) is the maximum deviation phase voltage from the average voltage value):
M axDeviation(U
:
value =
Average(U , U
12

U /U < 10% → 0%
xy e

U = value ≥ 20 → 20%
imbalance
value < 20 → value

Total Harmonic Distortion

This function measures harmonic distortions in the connected mains and provides a value for Total Harmonic Distortion THD. Har-
monic distortions can be caused by variable speed drives or other electronic devices. High harmonics can result in accelerated de-
gradation of insulation and loss of service life of a motor. In case of distortions above the adjustable warnlevel, it is recommended
to check the supply mains for faults or noisy equipment. The THD is defined as the ratio of the sum of the powers of all harmonic
components to the power of the fundamental frequency.
A threshold can be set to trigger a warning if the THD is too high.
>
U > U high
&
warn level
U > U high
&
trip level
U < U low
&
warn level
U < U low
&
trip level
U > U imb.
imb &
warn level
U > U imb.
imb &
trip level
&
THD >
&
warn level
, U , U )
12 23 31
, U ))
23 31


U high
Overvoltage Warn
warn delay
U high
Overvoltage Trip
trip delay
U low
Undervoltage Warn
warn delay
U low
Undervoltage Trip
trip delay
U imb.
Voltage Imb. Warn
warn delay
U imb
Voltage Imb. Trip
trip delay
Voltage Phase
Delay
1)
Loss
THD warn
51