Current through Reg. 50, No. 13; March 28, 2025
(a) Purpose.
The purpose of this section is to describe the requirements and procedures for
safe and effective connection and operation of distributed generation.
(1) A customer may operate 60 Hertz (Hz),
three-phase or single-phase generating equipment, whether qualifying facility
(QF) or non-QF, in parallel with the utility system pursuant to an
interconnection agreement, provided that the equipment meets or exceeds the
requirements of this section.
(2)
This section describes typical interconnection requirements. Certain specific
interconnection locations and conditions may require the installation and use
of more sophisticated protective devices and operating schemes, especially when
the facility is exporting power to the utility system.
(3) If the utility concludes that an
application for parallel operation describes facilities that may require
additional devices and operating schemes, the utility shall make those
additional requirements known to the customer at the time the interconnection
studies are completed.
(4) Where
the application of the technical requirements set forth in this section appears
inappropriate for a specific facility, the customer and utility may agree to
different requirements, or a party may petition the commission for a good cause
exception, after making every reasonable effort to resolve all issues between
the parties.
(b) General
interconnection and protection requirements.
(1) The customer's generation and
interconnection installation must meet all applicable national, state, and
local construction and safety codes.
(2) The customer's generator shall be
equipped with protective hardware and software designed to prevent the
generator from being connected to a de-energized circuit owned by the
utility.
(3) The customer's
generator shall be equipped with the necessary protective hardware and software
designed to prevent connection or parallel operation of the generating
equipment with the utility system unless the utility system service voltage and
frequency is of normal magnitude.
(4) Pre-certified equipment may be installed
on a company's utility systems in accordance with an approved interconnection
control and protection scheme without further review of their design by the
utility. When the customer is exporting to the utility system using
pre-certified equipment, the protective settings and operations shall be those
specified by the utility.
(5) The
customer will be responsible for protecting its generating equipment in such a
manner that utility system outages, short circuits or other disturbances
including zero sequence currents and ferroresonant over-voltages do not damage
the customer's generating equipment. The customer's protective equipment shall
also prevent unnecessary tripping of the utility system breakers that would
affect the utility system's capability of providing reliable service to other
customers.
(6) For facilities
greater than two megawatts (MW), the utility may require that a communication
channel be provided by the customer to provide communication between the
utility and the customer's facility. The channel may be a leased telephone
circuit, power line carrier, pilot wire circuit, microwave, or other mutually
agreed upon medium.
(7) Circuit
breakers or other interrupting devices at the point of common coupling must be
capable of interrupting maximum available fault current. Facilities larger than
two MW and exporting to the utility system shall have a redundant circuit
breaker unless a listed device suitable for the rated application is
used.
(8) The customer will furnish
and install a manual disconnect device that has a visual break that is
appropriate to the voltage level (a disconnect switch, a draw-out breaker, or
fuse block), and is accessible to the utility personnel, and capable of being
locked in the open position. The customer shall follow the utility's switching,
clearance, tagging, and locking procedures, which the utility shall provide for
the customer.
(c)
Prevention of interference. To eliminate undesirable interference caused by
operation of the customer's generating equipment, the customer's generator
shall meet the following criteria:
(1)
Voltage. The customer will operate its generating equipment in such a manner
that the voltage levels on the utility system are in the same range as if the
generating equipment were not connected to the utility's system. The customer
shall provide an automatic method of disconnecting the generating equipment
from the utility system if a sustained voltage deviation in excess of +5.0 % or
-10% from nominal voltage persists for more than 30 seconds, or a deviation in
excess of +10% or - 30% from nominal voltage persists for more than ten cycles.
The customer may reconnect when the utility system voltage and frequency return
to normal range and the system is stabilized.
(2) Flicker. The customer's equipment shall
not cause excessive voltage flicker on the utility system. This flicker shall
not exceed 3.0% voltage dip, in accordance with Institute of Electrical and
Electronics Engineers (IEEE) 519 as measured at the point of common
coupling.
(3) Frequency. The
operating frequency of the customer's generating equipment shall not deviate
more than +0.5 Hertz (Hz) or -0.7 Hz from a 60 Hz base. The customer shall
automatically disconnect the generating equipment from the utility system
within 15 cycles if this frequency tolerance cannot be maintained. The customer
may reconnect when the utility system voltage and frequency return to normal
range and the system is stabilized.
(4) Harmonics. In accordance with IEEE 519
the total harmonic distortion (THD) voltage shall not exceed 5.0% of the
fundamental 60 Hz frequency nor 3.0% of the fundamental frequency for any
individual harmonic when measured at the point of common coupling with the
utility system.
(5) Fault and line
clearing. The customer shall automatically disconnect from the utility system
within ten cycles if the voltage on one or more phases falls below - 30% of
nominal voltage on the utility system serving the customer premises. This
disconnect timing also ensures that the generator is disconnected from the
utility system prior to automatic re-close of breakers. The customer may
reconnect when the utility system voltage and frequency return to normal range
and the system is stabilized. To enhance reliability and safety and with the
utility's approval, the customer may employ a modified relay scheme with
delayed tripping or blocking using communications equipment between customer
and company.
(d)
Control, protection and safety equipment requirements specific to single phase
generators of 50 kilowatts (kW) or less connected to the utility's system.
Exporting to the utility system may require additional operational or
protection devices and will require coordination of operations with the host
utility. The necessary control, protection, and safety equipment specific to
single-phase generators of 50 kW or less connected to secondary or primary
systems include an interconnect disconnect device, a generator disconnect
device, an over-voltage trip, an under-voltage trip, an over/under frequency
trip, and a synchronizing check for synchronous and other types of generators
with stand- alone capability.
(e)
Control, protection and safety equipment requirements specific to three-phase
synchronous generators, induction generators, and inverter systems. This
subsection specifies the control, protection, and safety equipment requirements
specific to three phase synchronous generators, induction generators, and
inverter systems. Exporting to the utility system may require additional
operational or protection devices and will require coordination of operations
with the utility.
(1) Three phase synchronous
generators. The customer's generator circuit breakers shall be three-phase
devices with electronic or electromechanical control. The customer is solely
responsible for properly synchronizing its generator with the utility. The
excitation system response ratio shall not be less than 0.5. The generator's
excitation system(s) shall conform, as near as reasonably achievable, to the
field voltage versus time criteria specified in American National Standards
Institute Standard C50.13-1989 in order to permit adequate field forcing during
transient conditions. For generating systems greater than two MW the customer
shall maintain the automatic voltage regulator (AVR) of each generating unit in
service and operable at all times. If the AVR is removed from service for
maintenance or repair, the utility's dispatching office shall be
notified.
(2) Three-phase induction
generators and inverter systems. Induction generation may be connected and
brought up to synchronous speed (as an induction motor) if it can be
demonstrated that the initial voltage drop measured on the utility system side
at the point of common coupling is within the visible flicker stated in
subsection (c)(2) of this section. Otherwise, the customer may be required to
install hardware or employ other techniques to bring voltage fluctuations to
acceptable levels. Line-commutated inverters do not require synchronizing
equipment. Self-commutated inverters whether of the utility-interactive type or
stand-alone type shall be used in parallel with the utility system only with
synchronizing equipment. Direct-current generation shall not be operated in
parallel with the utility system.
(3) Protective function requirements. The
protective function requirements for three phase facilities of different size
and technology are listed below.
(A)
Facilities rated ten kilowatts (kW) or less must have an interconnect
disconnect device, a generator disconnect device, an over-voltage trip, an
under-voltage trip, an over/under frequency trip, and a manual or automatic
synchronizing check (for facilities with stand alone capability).
(B) Facilities rated in excess of 10 kW but
not more than 500 kW must have an interconnect disconnect device, a generator
disconnect device, an over- voltage trip, an under-voltage trip, an over/under
frequency trip, a manual or automatic synchronizing check (for facilities with
stand alone capability), either a ground over-voltage trip or a ground
over-current trip depending on the grounding system if required by the company,
and reverse power sensing if the facility is not exporting (unless the
generator is less than the minimum load of the customer).
(C) Facilities rated more than 500 kW but not
more than 2,000 kW must have an interconnect disconnect device, a generator
disconnect device, an over- voltage trip, an under-voltage trip, an over/under
frequency trip, either a ground over-voltage trip or a ground over-current trip
depending on the grounding system if required by the company, an automatic
synchronizing check (for facilities with stand alone capability) and reverse
power sensing if the facility is not exporting (unless the facility is less
than the minimum load of the customer). If the facility is exporting power, the
power direction protective function may be used to block or delay the under
frequency trip with the agreement of the utility.
(D) Facilities rated more than 2,000 kW but
not more than 10,000 kW must have an interconnect disconnect device, a
generator disconnect device, an over- voltage trip, an under-voltage trip, an
over/under frequency trip, either a ground over-voltage trip or a ground
over-current trip depending on the grounding system if required by the company,
an automatic synchronizing check and AVR for facilities with stand alone
capability, and reverse power sensing if the facility is not exporting (unless
the facility is less than the minimum load of the customer). If the facility is
exporting power, the power direction protective function may be used to block
or delay the under frequency trip with the agreement of the utility. A
telemetry/transfer trip may also be required by the company as part of a
transfer tripping or blocking protective scheme.
(f) Facilities not identified. In
the event that standards for a specific unit or facility are not set out in
this section, the company and customer may interconnect a facility using
mutually agreed upon technical standards.
(g) Requirements specific to a facility
paralleling for sixty cycles or less (closed transition switching). The
protective devices required for facilities ten MW or less which parallel with
the utility system for 60 cycles or less are an interconnect disconnect device,
a generator disconnect device, an automatic synchronizing check for generators
with stand alone capability, an over-voltage trip, an under-voltage trip, an
over/under frequency trip, and either a ground over-voltage trip or a ground
over-current trip depending on the grounding system, if required by the
utility.
(h) Inspection and
start-up testing. The customer shall provide the utility with notice at least
two weeks before the initial energizing and start-up testing of the customer's
generating equipment and the utility may witness the testing of any equipment
and protective systems associated with the interconnection. The customer shall
revise and re-submit the application with information reflecting any proposed
modification that may affect the safe and reliable operation of the utility
system.
(i) Site testing and
commissioning. Testing of protection systems shall include procedures to
functionally test all protective elements of the system up to and including
tripping of the generator and interconnection point. Testing will verify all
protective set points and relay/breaker trip timing. The utility may witness
the testing of installed switchgear, protection systems, and generator. The
customer is responsible for routine maintenance of the generator and control
and protective equipment. The customer will maintain records of such
maintenance activities, which the utility may review at reasonable times. For
generation systems greater than 500 kW, a log of generator operations shall be
kept. At a minimum, the log shall include the date, generator time on, and
generator time off, and megawatt and megavar output. The utility may review
such logs at reasonable times.
(j)
Metering. Consistent with Chapter 25, Subchapter F of this title (relating to
Metering), the utility may supply, own, and maintain all necessary meters and
associated equipment to record energy purchases by the customer and energy
exports to the utility system. The customer shall supply at no cost to the
utility a suitable location on its premises for the installation of the
utility's meters and other equipment. If metering at the generator is required
in such applications, metering that is part of the generator control package
will be considered sufficient if it meets all the measurements criteria that
would be required by a separate stand alone meter.