GRID-CONNECTED PHOTOVOLTAIC SYSTEM OF CUSTOMER’S INSTALLATION
CONNECTED AT LOW VOLTAGE - POWER QUALITY
The power quality (PQ) requirements at the electricity supply network point of common
coupling (PCC) are covered in the Energy Market Authority (EMA)’s Handbook for
Photovoltaic (PV) Systems and the Transmission Code. The PCC is the point in the
distribution network, electrically nearest to a connected person’s (definition refer to
Transmission Code) installation, at which other customers’ loads are, or may be, connected.
The EMA’s Handbook for PV Systems and Transmission Code can be found at EMA’s
website www.ema.gov.sg.
1
Technical Requirements
1.1
Harmonics
The generation of harmonics by the PV Systems shall not cause the maximum total
harmonic voltage distortion at the PCC to exceed total harmonic voltage distortion of
5%, with no individual odd harmonic greater than 4% and no individual even
harmonic greater than 2%. These limits include existing levels of harmonic distortion
at PCC.
1.2
Voltage Fluctuations including Flicker
The connection of the PV Systems shall not cause voltage fluctuation at the PCC to
exceed 3% of the nominal voltage. The connection of the PV Systems shall also
comply with Engineering Recommendation P28 – that is it shall not cause the shortterm severity value Pst and the long-term severity value Plt at the PCC to exceed 1.0
and 0.8 respectively.
1.3
Voltage Unbalance
The connection of the PV Systems shall not cause the maximum negative phase
sequence component of phase voltage at the PCC to exceed 1%.
1.4
DC Injection
DC injection into the distribution network is deprecated. DC injection into the
distribution network at the PCC shall not exceed 20mA under normal operating
condition, and not more than 0.5% of the PV inverter rating under any abnormal
operating conditions, with a maximum cap limit of 100mA. The Licensed Electrical
Worker (LEW) shall submit technical justification (including effect on the distribution
network) to SP PowerGrid (SPPG) for consideration, if their PV system DC injection
to the PCC deviates from this requirement.
1.5
Voltage Disturbance
The design operation of the PV systems shall take into consideration of voltage
disturbance phenomenon such as voltage dip in the distribution network.
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2
Submission of Compliance
The LEW shall confirm compliance with regard to the PQ requirements specified in
Clause 1. This shall include but not limited to the following:
•
•
•
•
Letter confirming compliance
Supporting data on power quality compliance
Single line drawing of the PV systems connected to the switchboard of
customer installation
Any other technical documentation deemed necessary by SPPG officer in the
course of clarification
The above should be submitted to SPPG at the time of application to connect to the
distribution network or 2 weeks after the clarification with the SPPG officer.
Technical justification shall be submitted to SPPG for consideration for deviation or
non-compliance, if any.
3
Power Quality Measurement at the Connected Person’s Premises
Where deemed necessary by SPPG, SPPG may carry out measurements at the
connected person’s incoming switchboard to verify the compliance report submitted
under Clause 2. The connected person shall make provision at their incoming
switchboard to facilitate the connection of SPPG’s power quality monitor. All
connection and disconnection of SPPG’s power quality monitor from the switchboard
shall be carried out by the LEW. The monitoring schedule shall be jointly agreed by
both parties. The monitoring period shall cover before PV system turn on and after
PV System turn on. The monitoring period will be for a period of minimum 7-day.
Before the commencement of this work, the connected person would have to agree
and sign SPPG’s testing/measurement services agreement. Alternatively, the LEW
can carry out their measurements verifying the declared compliance for submission.
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INFORMATION TO BE SUBMITTED
The LEW responsible for the installation shall complete and submit the following to SPPG,
Power Quality and Transient Management (PQTM) Section.
1
General Information
State the level of supply voltage intake, and any non-compliance with the power quality
requirements as specified in Clause 1 of the “Grid-Connected Photovoltaic System Of
Customer’s Installation Connected At Low Voltage - Power Quality”.
2
Harmonics
2.1
State the Harmonic current (1st harmonic order to 50th harmonic order) contributed by
the PV Systems at point of common coupling (PCC) to the SP PowerAssets’
electricity supply network.
2.2
For installations that have non-linear loads in addition to the PV Systems, 2 set of
harmonic current data to be provided. One set as above, and the other set shall be
for aggregation of the harmonic current injection at the PCC.
3
Voltage Fluctuation and Flickering
3.1
State maximum voltage fluctuation (voltage step change in % of nominal voltage) at
the PCC in relation to PV Systems connection and operation.
3.2
Flicker levels at the PCC:
Pst during PV Systems starting
Plt during PV Systems starting
Pst during PV Systems normal operation
Plt during PV Systems normal operation
4
Voltage Unbalance
State maximum voltage unbalance (% of nominal voltage) at the PCC in relation to
PV Systems connection and operation.
5
DC Injection
Maximum DC injected into the network from the PV
Systems during normal and abnormal operating
conditions
Normal Condition
=
mA
Abnormal Condition =
mA
Mains Isolation Transformer installed for PV Systems?
Yes / No
DC injection detection device installed for PV Systems?
Yes / No
Note:(1) Isolation transformer installed, if any - please provide nameplate information, e.g.
KVA, voltage rating etc.
(2) DC injection detection device installed, if any - please provide DC injection trip
setting for the PV Systems.
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