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18
ANSI MEDIUM VOLTAGE METAL- CL AD DIGITAL SWITCHGEAR
—
Primary testing-current sensors
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All current and voltage sensors can remain
27 Primary test system
connected to the bus during power frequency
CPC 100 from Omicron
(bus hipot) and secondary wire dielectric testing.
Primary testing is valuable for verification of the
whole measurement chain in the application
including switching equipment (circuit breaker or
contactor). The measuring chain includes the
sensor, cable connections and settings of the
protection relay.
Digital solution vs. traditional switchgear
The following applies in the case of digital
switchgear:
• No complex checks of inter-panel wiring are
required
• Ethernet network fault detection is available
• Higher protection relay engineering skills are
required in case of modifications
• Relay configuration modifications can be
performed using the free downloadable
PCM600 software
• For pre-testing, secondary tester with sensor
support (low voltage output signals) is required
• The setting of sensors in the protection relay is
described in the Digital Switchgear Engineering
guide 1VAL108402-TG Rev A
Recommended primary testing device
For primary current and voltage injection you can
use the same devices as with conventional
switchgear. There are multifunctional primary
test systems, such as the Omicron CPC 100
(Figure 27), available on the market which enables
entering sensor correction factors and the
display of the corrected value for both current
and voltage sensors.
Introduction of CPC 100 – key features:
• Supply up to 800 A or 2000 V with max. 5 kVA
power output, over a frequency range of 15 Hz –
400 Hz or 400 A DC
• Supply up to 2000 A or 12 kV using external
current or voltage amplifiers
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27
Current sensors
Primary testing verifies the whole measurement
chain including the sensor, cable connections and
settings of the protection relay. Each current
sensor has unique physical polarity. Therefore, no
polarity (physical test) is needed. The current
sensor polarity can be changed via the relay
parameter setting. Secondary winding resistance
and magnetization curve tests are not applicable
either.
All current sensors are tested individually during
routine production tests for output accuracy and
determination of the ratio correction factors.
Production test reports are available for all
sensors and are provided when requested. It is
not required to test the sensors separately from
the entire chain.
If it is desired to test only the sensors, separate
from the entire circuit, then follow only the steps
shown below that are necessary to establish a
primary current injection circuit and then connect
a measurement device to the RJ45 connectors of
the sensor outputs. Please note that the
measurement and power supply devices are
suggested devices. Performance characteristics
are stated in case the user wants to use alternate
power supply and measuring devices.
The measurement device should have a
measurement range of 5 mV to 20 V, with an
accuracy of +/-0.1% or better.
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