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

7.2.2 Knowledge of the electrical circuit
It is important to consider the entire electrical environment prior to connecting a monitoring device. This can
best be done by drawing or obtaining a single-line diagram of the electrical circuit being monitored. This
single-line sketch may encompass the utility service, neighboring electrical customers, and internal wiring
and loads. Awareness of this environment will facilitate consideration for safety, proper connection, and
interpretation of data. Some speciÞc items to include on the diagram are described below.
In order to maintain reliability, a utility sometimes has more than one alternative for feeding electrical
service to a particular area. Both the normal and alternate utility distribution circuits should be identiÞed.
These circuits can then be examined for devices that may produce events on a monitor during operation. 
Electrical loads at neighboring facilities may affect the electrical quality at the monitoring site. Large indi-
vidual loads operated nearby should be identiÞed, as is practical. The proximity and type of interface
between this equipment and the monitoring site will determine the severity of the effect. For example, if the
neighbor is served from the same electrical transformer, then there is a direct path between the two end

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IEEE
MONITORING ELECTRIC POWER QUALITY
Std 1159-1995
39
users. Therefore, the magnitude of the electrical events associated with the neighborÕs equipment will be
greater than if it were somewhat isolated by service through a separate transformer.
Construction that is located near a monitoring site should also be considered. Often local connection stan-
dards are different between temporary and permanent electrical service. The temporary service may have
more or less isolation. In either case, the type of construction equipment to be operated during a monitoring
period should be considered.
Due to proximity, electrical equipment and the mechanical aspects of electrical distribution at a monitoring
location will have the greatest effect on electrical quality. Close examination from the main electrical feed to
the end-use equipment is a prerequisite to monitoring. This entire system should be inspected for clean, tight
connections. This will resolve many problems. This inspection should also include making a log of devices
and equipment throughout the circuits to serve as a reference when interpreting the data. Especially, the con-
nection and operation schedule of backup power sources and mitigating devices such as uninterruptible
power supplies should be determined.