Ieee std 1159-1995, ieee recommended Practice for Monitoring Electric Power Quality

7.2.4 Facility power quality survey
A power quality survey of an entire facility usually starts as far upstream in the electrical distribution as
possible. Prior to monitoring, a thorough check of the mechanical condition of important electrical circuits
should be completed. It is usually unnecessary to monitor circuits greater than 480 V unless loads are
directly connected to those higher voltages. The initial monitor location is typically the secondary side of the
main service transformer. This location is generally 600 V class service equipment. It may also be useful to
monitor simultaneously at more than one location within a facility.
If monitoring of higher voltages is required, then special voltage divider circuits or PTs and clamp-on CTs
may be required. These transducers should have a frequency response that permits the capture of transient
disturbances. Existing voltage transformers and CTs, used for metering, may not have the frequency
response to provide power monitors with accurate transient information. They can be used by a power mon-
itor, however, to record low frequency voltage ßuctuations at the distribution level voltage. Special safety
rules apply to working with greater than 600 V class service equipment.
7.2.5 IEEE Std 519-1992
IEEE Std 519-1992 [B13] recommends harmonic current injection and voltage distortion guidelines. To
monitor for distortion levels related to these guidelines, the harmonics monitor should be placed at the point
of common coupling as speciÞed in the standard.

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IEEE
MONITORING ELECTRIC POWER QUALITY
Std 1159-1995
41
7.2.6 PT and CT speciÞcations
7.3 Equipment connection
7.3.1 Sense inputs
The monitoring analyzer should be connected in a manner that does not violate manufacturerÕs recommen-
dations for voltage or current limits. In accordance with 7.1, the installation must be completed in a
safe manner.
The sense lead connections in any monitoring will have to cover all disturbance modes that could impact the
proposed devices. As the number of circuit conductors increases, the necessary monitoring modes will also
increase. For example, if the device is powered by a 120 V plug without an equipment grounding conductor
(such as audio visual equipment for household use) phase-to-neutral monitoring is the only valid conÞgura-
tion, whereas a 120 V rms plug with an equipment grounding conductor should be monitored in a phase-to-
neutral, phase-to-ground, and neutral-to-ground conÞguration. A three-phase data processing unit with inter-
connected single-phase peripherals may have to be monitored phase-to-phase, phase-to-neutral, phase-to-
ground, and neutral-to-ground. The number of monitoring modes could be reduced through awareness of the
deviceÕs capability to withstand these different modes of disturbance.
The best mode in which to connect to three-phase loads is to match the conÞguration of the affected equip-
ment. If the sensitive equipment, for example, is connected in delta (three wire without a neutral), the moni-
tor should be conÞgured likewise. A phase-to-ground channel should be included if possible. If the sensitive
equipment is connected in wye, the analyzer should be conÞgured in wye as well, and a neutral-to-ground
reference should be included.