B
Appendix
EPQ DataNode Series User’s Guide
B-11
response, even at 60 Hz, may be dependent on current magnitude, temperature, and secondary cable length. This makes
this device very difficult to use for accurate power quality monitoring.
In general, all primary sites should be monitored with metering class VTs and CTs to obtain accurate results over the
required frequency spectrum. Installation will require a circuit outage but convenient designs can be developed for pole
top installations.
Another option for monitoring primary sites involves monitoring at the secondary of an unloaded distribution trans-
former. This will give accurate results up to at least 3 kHz. This option does not help with the current transducers, but it
is possible to get by without the currents at some circuit locations (e.g. end of the feeder). This option may be particular-
ly attractive for underground circuits where the monitor can be installed on the secondary of a pad-mounted transformer.
Primary wound CTs are available from a variety of CT manufacturers.
Secondary Sites
Transducer requirements at secondary sites are much simpler. Direct connection for the voltage is possible for 120/208
Volt RMS or 277/480 Volt RMS systems. This permits full utilization of the instrument's frequency response capability.
Currents can be monitored with either metering CTs (at the service entrance, for example), or with clamp-on CTs (at
locations within the facility). Clamp-on CTs are available in a wide range of turns ratios.
Table 1 VT and CT Options describe the different power quality and the proper transducers to measure the type of power
quality problem.
Table 1 VT and CT Options
Monitoring
Location
Voltage
Transducer
Current
Transducer
Substation
M etering V Ts
Special purpose capacitive
or resistive dividers
C alibrated bushing taps
M etering C Ts
R elaying C Ts
O verhead lines
M etering V Ts
M etering C Ts
U nderground
locations
M etering V Ts
Pad m ounted transform er
Special purpose dividers
M etering C Ts
Secondary Sites
Service Entrance
In Facility
D irect connection
D irect connection
M etering C Ts
C lam p-on C Ts
C lam p-on C Ts
