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Field Instruction
3.26 Private Parallel Generators – General Operating Guidelines
Purpose
This instruction provides general information and operating guidelines for the use of PPGs, by
setting out the minimum requirements for the installation and connection of Remote Disconnection
Base Unit(s) to the Low Voltage mains.
Before the commencement of work, a risk assessment must be carried out to identify and
document the hazards and risks associated with the task and ensure appropriate control measures
are put in place.
The appropriate PPE must be worn, see (Section 2 Safety Field Instructions 2.1, 2.2, 2.5 and
FI 2.6 Worksite Clothing / PPE Requirements) in this manual.
Instruction
Network Connection

PPGs can usually be connected to many alternate feeders.

Alternative connection paths should not be used without due consideration of auto recluse
or auto changeover schemes that may be enabled, unless the Facilities generation
equipment is isolated from the Network.
Horizon Power Protection
HP Feeder circuit breakers and field reclosers connected to PPGs will typically have some or all of
the following protection or similar:

Over-Current and Earth Fault.

Automatic Reclose.

Live Line Blocking or No-Volt check before closing (not required if ‘out of sync’ fault level is
less than 2kA).

Check-Sync before closing (uncommon).

Intertrip from HP normally connected feeder circuit breaker to disconnect PPG generating
equipment.
The relevant protection for each site should be checked and understood before commencing any
switching.
Note:
Pole Top Switches and Ring Main Units etc are not normally fitted with any protection to prevent
unsynchronised switching.
CS10 # 2225919
3.26 Private Parallel Generators – General Operating Guidelines
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Field Instruction
PPG Control and Protection
PPGs will typically have some or all of the following control and protection or similar:

Over-Current and Earth Fault.

Check-Sync.

Over and Under Voltage.

Over and Under Frequency.

Rate of Change of Frequency.

Export (or Import) Power or Current.

Pole Slip.

Inter-trip from HP Feeder Circuit Breaker to isolate the PPG generating equipment from the
HPC Network.

‘Enable’ signal from HPCC to allow PPG to synchronise generating equipment and connect
to HPC Network.

‘Trip’ signal from HPCC to isolate the PPG generating equipment from the HPC Network.
General
Connection to the network
Connecting the PPG to the Network shall always be done at a point where Check-Sync facilities
are available (usually at the PPG), or else an out of synchronism fault could result in serious
damage to plant and injury to personnel. For example, a typical pole top switch or RMU must never
be closed in order to energise a PPG.
The Facilities shall not be permitted to supply other Horizon Power customers while generating in
island mode under any circumstances. (It is possible for Horizon Powers switching operations to
result in PPGs becoming disconnected from the Network).
Connection (or re-connection) of PPGs to the Network shall not be permitted until any fault
restoration or corrective work is complete, all HPCC and Customer protection and control
equipment is operational and the Horizon Power Network is stable.
To enable the PPG to be reconnected to the Network upon the customers requestion, HPCC shall
send an ‘Enable’ signal from the SCADA.
Auto Reclose
Any circuit breaker or recloser within the connection path to a PPG shall have reclose functions
disabled (and tagged on SCADA), unless the device has Live Line Blocking or Check-Sync
protection ‘Enabled’.
Trips and Inter-Trips
If necessary, a PPG may be tripped off from SCADA. Generally, a ‘Trip’ signal from SCADA will
cause the CMS to trip (or on some installations cause the GMS to trip if both the GMS and the
CMS are closed) to isolate the PPG generating equipment from the Network.
CS10 # 2225919
3.26 Private Parallel Generators – General Operating Guidelines
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Field Instruction
Whenever practicable before sending a ‘Trip’ signal, the customer shall be given adequate notice
to arrange for supply to their internal loads.
Maintenance and Alternate Connections
Inter-trips from the normally connected feeder circuit breaker should be disabled if a PPG is
connected to an alternate feeder, or if circuit breaker/protection maintenance is being performed.
Switching Operations and Supply Restoration
In the event of any loss of supply to a PPG (e.g. A feeder or recloser tripping or a Pole Top Switch
being inadvertently opened), the following switching guidelines shall be observed:

No switching operations on any feeder connection to the PPG shall be performed prior to
confirming that the PPG generation equipment has been disconnected from the Network
(send a ‘Trip’ command from SCADA to the PPG if necessary).

While restoration work on the Network is carried out, either the GMS or the CMS must be
open. If the CMS is open the PPGs generation equipment may be run islanded to supply
PPG internal loads only.

Investigate if any switching program are in progress in the area and contact the relevant
staff.

Re-connection of the PPG to the Network shall not be permitted until any fault restoration or
corrective work is complete, all HP and Customer protection and control equipment is
operational and the Horizon Power Network is stable.
CS10 # 2225919
3.26 Private Parallel Generators – General Operating Guidelines
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