Dielectric Strength Testing - GE 239 Instruction Manual

CHAPTER 2: INSTALLATION
2.1.4

Dielectric Strength Testing

239 MOTOR PROTECTION RELAY – INSTRUCTION MANUAL
Courtesy of NationalSwitchgear.com
GROUNDING
• SAFETY GROUND (13): Connect the safety ground terminal 13 to a reliable system
ground within the starter using heavy gauge wire. For safety, all metal parts within the
239 are connected to this ground terminal. Shield terminals 20/48 and RTD COM
terminals 51/54/57 are internally connected to the safety ground, terminal 13.
• FILTER GROUND (14): Using #12 gauge wire or ground braid, connect this terminal to
a solid system ground, typically a copper bus in the starter. Extensive filtering and
transient protection is built into the 239 to ensure reliable operation under harsh
industrial operating environments. Transient energy must be conducted back to the
source through filter ground terminal 14. The filter ground terminal is separated from
the safety ground terminal to allow dielectric testing of a starter with a 239 wired up.
When properly installed, the 239 will meet the interference immunity requirements of IEC
801 and ANSI C37.90.
It may be required to test a complete motor starter for dielectric strength with the 239
installed. This is also known as "flash" or "hipot" testing. The 239 is rated for 1530 V AC
isolation for 1 minute (or 1836 V AC for 1 second) between relay contacts, CT inputs, control
power inputs and safety ground terminal 13. Some precautions are necessary to prevent
damage to the 239 during these tests.
Filter networks and transient protection clamps are used between the control power, serial
port, switch inputs, analog output, thermistor, RTDs inputs and the filter ground terminal
14 to filter out high voltage transients, radio frequency interference (RFI) and
electromagnetic interference (EMI). The filter capacitors and transient absorbers could be
damaged by the continuous high voltages relative to ground that are applied during
dielectric strength testing. Disconnect the filter ground terminal 14 during testing of the
control power inputs. Relay contact and CT terminals do not require any special
precautions. Do not dielectric strength test the serial port, thermistor, RTD or analog
output terminals else the 239 internal circuitry will be damaged.
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