15
The TEV measurement mode also needs to refer to the pulse count value P /
Cycle, and the pulse number and amplitude comprehensively measure the
health of the switchgear.
When the environmental value is large, the source of interference needs to be
found. The interference source of TEV is different from ultrasonic waves.
Ultrasonic interference is generally limited to a limited space, while TEV
interference affects the entire space through radio frequency, such as welding
machines, inverters, walkie-talkies, Compared with ultrasonic interference,
wireless broadcasting stations, etc., such interference signals are sometimes
difficult to avoid or clear, so it is recommended to use the ultrasonic method to
measure when the environment (interference) value is detected to be large.
The TEV test data can be judged according to Table 3, there will be slight
discrepancies in different regions, but the difference is not much.
TEV reading
Explanation
High background reading, ie greater than 20dB
Note: The background reading refers to the reading when
the sensor is not attached to the cabinet.
(a) High levels of noise may mask the discharge in the
switchgear;
(b) It may be due to external influences, and the external
interference source should be eliminated as much as possible
before retesting, or use a partial discharge monitor to identify
any discharge in the switchgear.
All readings of switchgear and background reference are
less than 20dB.
No partial discharge. Recheck once a year.
The reading is 20 ~ 29dB
The device is slightly partially discharged
The reading is 29 ~ 40dB
The equipment has medium-level local discharge, which
should be reported to the team or special responsibility to
shorten the inspection cycle
The reading is 40 ~ 50dB
There is serious partial discharge of the equipment. It should
be reported to the team or special responsibility to shorten the
inspection cycle. When there is a motor stop, the source of the
partial discharge should be checked.
The reading is 50 ~ 60dB
There is serious partial discharge of the equipment, you should