The Role of Distributed Generation in Power Quality and Reliability

minimum acceptable (Minimum) and desirable (Objective) levels of reliability. Reliability is
gauged utilizing indices for both the frequency and duration of service interruptions. The
recommended reliability levels are customized for each of the utility operating areas in the State.
The Order also includes criteria for identifying, ranking, and developing appropriate
improvement plans for the worst-performing circuits in each operating area. In addition, the
utilities are required to develop programs for responding to customers' power quality problems.
These reports have created a common set of metrics for defining the issue in terms of average
interruption frequency, average interruption duration, and average service restoration time.
Review of the PQRs from the major investor-owned utilities in the state shows that high/low
voltage excursions ranged from 160 to 281 incidents per year by region for one utility. Voltage
quality issues occurred thousands of times per year within each service region. Utilities have
also engaged in case studies and customer interviews in an attempt to better quantify the issues
and improve operations.
New York Customer Views of Power Quality and Utility Response
The project team spoke with nine facility managers in sensitive industries throughout New York
State about their power quality and reliability issues. While, the very dramatic extended
Northeast blackout of 2003 created problems for most of them, this once in 25 year event is not
as important as the more subtle and more frequent disturbances these facilities experience every
year, every summer, and, in some cases, nearly every day. Problems arise with computers,
microprocessors, fluorescent light ballasts, sensitive medical imaging equipment, variable speed
drives, computer directed design and manufacturing, critical communications equipment,
nuisance trips on circuit breakers, overheating of equipment, etc. Some facilities don’t know
what is causing their equipment to break, go off-line or lose data, they just go in and fix it to their
systems get back up and running. Other facilities have become very sophisticated in monitoring
their power signal and in diagnosing problems.
Still, from the perspective of the customers contacted for this study, utilities were generally not
helpful in identifying and diagnosing power quality problems. Consequently, to get to the root
of PQ related problems, customers had to install monitoring equipment and identify and diagnose
the problems themselves. Armed with such investigative data, some customers were then able to
get the utility to act to correct persistent low voltage or phase imbalance conditions.
All of them have made some level of power quality/reliability enhancing investments to protect
their operations. Both centralized and equipment level UPS systems were used. Power factor
correction, harmonic filters, isolation transformers, and other equipment were also used to
support specific facility issues. Most included standby generation as part of their protection
scheme. Two facilities had in-place and operating combined heat and power facilities and a
number of others had done CHP feasibility studies. Of the two operating CHP systems, one was
an integral part of the facility power-quality protection system. In the other case, the facility
manager was very interested in this issue but had been unable to install a system capable of
running independently of the grid due to restrictive utility interconnect requirements. He was
continuing to push the utility for addition of that capability to his DG system. One facility, in
Executive Summary ES8 The Role of DG in Power Reliability