NS194
Protection Requirements of Embedded Generators >30kW
December 2013
Amendments from: NSA1746 Jan 2014
SUMMARY
Network Standard NS194 outlines the requirements an Embedded Generator should fulfil
when connecting to the Ausgrid’s network.
ISSUE
For issue to all Ausgrid and Accredited Service Providers’ staff involved with the connection
of Embedded Generators to the network, and is for reference by field, technical and
engineering staff.
Ausgrid maintains a copy of this and other Network Standards together with updates and
amendments on www.ausgrid.com.au.
Where this standard is issued as a controlled document replacing an earlier edition, remove
and destroy the superseded document.
DISCLAIMER
As Ausgrid’s standards are subject to ongoing review, the information contained in this
document may be amended by Ausgrid at any time.
It is possible that conflict may exist between standard documents. In this event, the most
recent standard shall prevail.
This document has been developed using information available from field and other sources
and is suitable for most situations encountered in Ausgrid. Particular conditions, projects or
localities may require special or different practices. It is the responsibility of the local
manager, supervisor, assured quality contractor and the individuals involved to ensure that a
safe system of work is employed and that statutory requirements are met.
Ausgrid disclaims any and all liability to any person or persons for any procedure, process or
any other thing done or not done, as a result of this Standard.
Note that compliance with this Network Standard does not automatically satisfy the
requirements of a Designer Safety Report. The designer must comply with the provisions of
the WHS Regulation 2011 (NSW - Part 6.2 Duties of designer of structure and person who
commissions construction work) which requires the designer to provide a written safety
report to the person who commissioned the design. This report must be provided to Ausgrid
in all instances, including where the design was commissioned by or on behalf of a person
who proposes to connect premises to Ausgrid’s network, and will form part of the Designer
Safety Report which must also be presented to Ausgrid. Further information is provided in
Network Standard (NS) 212 Integrated Support Requirements for Ausgrid Network Assets.
INTERPRETATION
In the event that any user of this Standard considers that any of its provisions is uncertain,
ambiguous or otherwise in need of interpretation, the user should request Ausgrid to clarify
the provision. Ausgrid’s interpretation shall then apply as though it was included in the
Standard, and is final and binding. No correspondence will be entered into with any person
disputing the meaning of the provision published in the Standard or the accuracy of
Ausgrid’s interpretation.
Network Standard
NS194
Protection Requirements of Embedded Generators >30kW
December 2013
CONTENTS
1
SCOPE ........................................................................................................................ 1
2
REFERENCES ............................................................................................................ 1
3
APPLICATION FOR CONNECTION............................................................................ 3
4
EARTHING .................................................................................................................. 3
5
PROTECTION REQUIREMENTS................................................................................ 4
5.1
5.2
5.3
5.4
5.5
5.6
5.7
5.8
5.9
5.10
5.11
5.12
5.13
5.14
5.15
5.16
6
Network and LoM Protection System Redundancy ......................................... 7
Neutral Voltage Displacement (NVD) .............................................................. 7
Network and LoM Circuit Breaker Fail ............................................................. 7
Over and Under Voltage Protection ................................................................. 8
Over and Under Frequency Protection ............................................................ 8
Parallel Operation and Check Synchronisation (CS)....................................... 8
Fault Levels and Ausgrid Scheduling............................................................... 9
Loss of Mains (LoM) /Anti-Islanding................................................................. 9
Intertrip Communications Link........................................................................ 10
Automatic Switching and Reclosing............................................................... 10
Generator Automatic Reconnection............................................................... 10
Relay and Tripping Supplies .......................................................................... 11
Sydney Triplex Network ................................................................................. 11
Connection arrangement examples ............................................................... 11
Relay Requirements....................................................................................... 11
Approval of Protection Schemes.................................................................... 12
COMMISSIONING AND AUSGRID WITNESS TESTING.......................................... 13
APPENDIX 1 – SAMPLE PROTECTION SCHEMES .......................................................... 14
APPENDIX 2 – AUSGRID APPROVED PROTECTION RELAYS ....................................... 18
1
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December 2013
SCOPE
This document outlines the protection system requirements for connection of
Embedded Generation of greater than 30kW* to the Ausgrid network.
It does not deal with the protection requirements for network connected micro size
generators less than 30kW 3-phase or 10kW per phase or synchronised close
transfer systems which should comply with AS 4777 -2002 and the 2007 Service
and Installation Rules of NSW particularly Section 8, Alternative Sources of Low
Voltage Supply.
For example, an installation which consists of 4 separate arrays of PV, each having
a capacity of 10kW would be subject to the requirements of this Network Standard,
as the total electrical output of the installation is 40kW.
*The size of generator is defined as the combined total electrical output of all generating units
at the point of connection.
2
REFERENCES
Electrical construction works on Ausgrid’s low voltage and high voltage distribution
systems must be carried out in accordance with Ausgrid’s Supply Connection and
Network Standards and Australian Standards which include but are not limited to
the following:
ES 1
Premises Connection Requirements
ES 3
Metering Installations
ES 11
Requirements for the Connection of Embedded Generators
ENOS
Electricity Network Operating Standards
Policy for ASP/1 Premises Connection
Connection Policy – Connection Charges
NS116
Design Standards for Distribution Earthing
NS 194A
Guidelines for Photovoltaic installations up to 200kW connected via
inverters to the Ausgrid network
NS 194B
Guidelines for synchronous and asynchronous machines connected
to the Ausgrid network.
Generator Connection Agreement: General Conditions
The latest edition of the Service & Installation Rules of NSW
Ausgrid’s Electrical Safety Rules
Australian Standards such as:
AS/NZS 3000- Electrical Installations (Wiring Rules), 3010 – Electrical Installations
– Generating Sets, 3017 – Testing Guidelines
AS/NZS 3008 - Electrical Installations – Selection of Cables
AS 4777-2005 - Grid Connection of Energy Systems via Inverters, Parts1, 2, 3
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AS5033: Installation of Photovoltaic Arrays
AS 2467 – Maintenance of Electrical Switchgear
AS – 60038-2000 – Standard Voltages
AS/NZS 4853:2012- Electrical Hazards on metallic pipelines
AS/NZS 3835:2006 –Earth Potential Rise – Protection of telecommunications
network users, personnel and plant. Part 1 – Code of Practice
AS6100.3.2: Electromagnetic Compatibility – Limits for Harmonic Current Emissions
AS/NZS 61000.3.6 – Electromagnetic Compatibility (EMC) –Limits – Assessment of
emission limits for distorting loads in MV and HV power systems.
AS/NZS 61000.3.7 – Electromagnetic Compatibility (EMC) –Limits – Assessment of
emission limits for fluctuating loads in MV and HV power systems
Other references:
ENA DOC 001-2008 National Electricity Network Safety Code
ENA EG-0:2012 – Power System Earthing Guide Pt:1 Management Principles
IEEE PSRC
Intertie protection of consumer-owned sources of generation,
3MVA or less
IEEE 1547
IEEE Standard for interconnecting Distributed Resources with
Electric Power Systems
BCSE
Technical Guide for Connection of Renewable Generators to the
local Electricity Network
IEC 61000-3-14
“Assessment of emission limits for the connection of disturbing
installations to LV power system”
IEC 60255
Measuring Relays and Protection Equipment Requirements
ENA
ENA Guideline for the preparation for connection of Embedded
Generation within Distribution Networks – May 2011
Legislative and Electricity Market requirements:
NER
National Electricity Rules, including Central despatch and Integration
of Wind and Other Intermittent Generation Rule 2007.
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APPLICATION FOR CONNECTION
For procedure regarding the application for connection of generator greater than
30kW refer to ES-11 Requirements for Connection of Embedded Generators.
4
EARTHING
The customer is required to ensure that the generator installation has an earthing
system that has been designed to limit any step, touch and transferred potentials to
safe values using the principles detailed in “ENA EG-0:2012 – Power System
Earthing Guide Pt1: Management Principles”. Equipment used to interface to the
distribution network (e.g. step up transformer or circuit breaker) must comply with
NS116 – Design Standards for Distribution Earthing.
Additionally the earthing system of the Generator must be designed to limit the
voltages impressed onto surrounding utility infrastructure under earth fault
conditions. For metallic pipelines the tolerable voltages are listed in AS/NZS
4853:2012 and for telecommunications assets the voltage limits are found in
AS/NZS 3835:2006.
Generation schemes working in parallel with the distribution network in effect
become an integral part of the electricity distribution network. Therefore neutral
earthing arrangements for the private generators and any interconnection
transformers must be designed to suit the requirements of both the distribution
network and the customer’s generation installation and details provided to Ausgrid.
High Voltage Generators
The generator’s high voltage star point must be effectively isolated from earth (i.e.
isolated or earthed via a high impedance) to avoid any earth fault contributions
flowing into the Ausgrid system and to inhibit the flow of harmonic currents through
the neutral. Each case will be discussed with the Customer on its merits.
Low Voltage Generators
Generators connected to the network via a delta/star transformer with the delta on
the network side may have their neutral directly connected to earth (i.e. via an MEN
link).
Effective isolation of this neutral may be required to inhibit the flow of harmonics
through the neutral and the generator’s method to limit harmonics must be
discussed and agreed to by Ausgrid. The use of 4-pole switching may be required if
the generator can operate in standby mode.
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PROTECTION REQUIREMENTS
Protection systems for embedded generating units operating in parallel with the grid
can be divided into the following two main categories as described below. This
standard only covers the requirements for Network and Loss of Mains (LoM)
protection systems for embedded generators and does not cover the requirements
for short circuit protection systems in customer installations.
As required by NER Schedule 5.2.2, a “Generator must only apply settings to a
control system or a protection system that are necessary to comply with
performance requirements of schedule 5.2 if the settings have been approved in
writing by the relevant Network Service Provider and, if the requirement is one that
would involve AEMO under clause 5.3.4A(c) of the Rules, also by AEMO. A
Generator must not allow its generating unit to supply electricity to the power system
without such prior approval.”
Ausgrid will require all protection system schematics, relays and settings for the
generator protection systems described within this document as listed in Tables 4.1
and 4.2 to insure the installation complies with this standard. All protection
equipment must be tested and commissioned by a competent person to the agreed
settings and a Certificate of Compliance issued to Ausgrid prior to connection to the
Ausgrid network. The customer is to keep written records of all protection settings
and test results. A copy is also required by Ausgrid.
Short Circuit protection (Not covered in this standard)
Systems installed to protect equipment (the generating units and the power system)
against short-circuit faults.
The requirements for these systems in LV installations are not covered in this
standard, they are covered in AS3000.
The requirements for these systems in HV installations will be determined on a case
by case basis depending on the connection arrangement. Requirements for short
circuit protection are covered elsewhere in Australian and Ausgrid Standards.
Protection dealing with normal short-circuit faults is required, as for any customer
connection, but may need some special treatment to allow for multiple sources of
active power onto the network. Even if the generator is not a source of short-circuit
current, adequate short circuit protection is necessary as for any Customer
installation.
Network and Loss of Mains (LoM) protection (Covered by this standard)
Systems installed to ensure the network is operating within the limits of its design
and that uncontrolled ‘islands’ can not be formed between the generator and the
local or interconnected network. This standard specifically covers the requirements
for these types of protection schemes.
Protection shall be designed in accordance with the applicable regulations and
Ausgrid’s standards and network engineering guidelines, which require a main and
back-up set of protection to detect all credible Islanding Conditions. The protection
systems must include sufficient redundancy to ensure that the generator/s
disconnect from the network with any single protection element out of service or if
any single circuit breaker fails to operate. This will require a main and backup
protection scheme.
The protection schemes required are dependent on the type of generating units and
the point of connection to Ausgrid’s network. See Tables 5.1, 5.2 following.
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Table 5.1: Inverter-connected Generator Protection Requirements
Reference
Section
Low Voltage
Connection
Point (415V)
High Voltage
Connection Point
(11kV and above)
AS4777 compliant inverters
(Note 2, Note 3)
5.1
M
M
Neutral Voltage Displacement
5.2
Refer Sect 5.2
M
Under voltage and Overvoltage
5.4
M
M
Under frequency and Over
frequency
5.5
M
M
Ausgrid scheduling
5.7
Refer Sect 5.7
Refer Sect. 5.7
Protection and Associated
Reference
Common Requirements
No Export Generator Requirements (Note 1)
Grid Reverse Power
5.8
M1 (P)
M1 (P)
Grid Low Forward Power
5.8
M2
M2
5.8/9
M1 (P)
M1 (P)
5.8
M2
M2
Export Generator Requirements
Intertrip
ROCOF and Vector Shift
Legend
M:
Mandatory
M1, M2
Mandatory with alternative - select either ‘M1’ or ‘M2’ to suit the connection.
Option marked with (P) is preferred.
Note 1: In circumstances where reverse power and low forward power are not
suitable for use with No Export Generators, Intertrip or Vector Shift and
ROCOF LoM protection, as per Export Generator Requirements, can be
provided by agreement with Ausgrid.
Note 2: Inverters which are not AS4777 compliant will be required to be assessed
on a case by case basis.
Note 3: The AS4777 Inverters provide the main Network and LoM protection, so
the protection functions listed in Table 5.1 are the back-up protection
requirements. Refer to Section 5.1.
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Table 5.2: Synchronous Machine and Asynchronous Machine Generator
Protection Requirements
Reference
Section
Low Voltage
Connection
Point (415V)
High Voltage
Connection
Point (11kV
and above)
Neutral Voltage Displacement
5.2
Refer Sect 5.2
M
Circuit Breaker Fail
5.3
M
M
Duplicate Under voltage and
Overvoltage
5.4
M
M
Duplicate Under frequency and Over
frequency
5.5
M
M
Synchronising*
5.6
M
M
Ausgrid scheduling
5.7
Refer Sect 5.7
Refer Sect. 5.7
Protection and Associated
Reference
Common Requirements
No Export Generator Requirements (Note 1)
Grid Reverse Power and Grid Low
Forward Power
5.8
M1 (P)
M1 (P)
Duplicate Grid reverse power
5.8
M2
M2
5.8/9
M1 (P)
M1 (P)
5.8
M2
M2
Export Generator Requirements
Intertrip
Duplicate ROCOF and Vector Shift
Legend
M
Mandatory
M1, M2
Mandatory with alternative - select either ‘M1’, ‘M2’ to suit the connection.
Option marked with (P) is preferred by Ausgrid.
* Asynchronous machines do not require synchronising facilities.
Note 1:
In circumstances where reverse power and low forward power are not
suitable for use with No Export Generators, Intertrip, Vector shift and
ROCOF LoM protection, as per the Export Generator Requirements,
can be provided by agreement with Ausgrid.
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5.1
December 2013
Network and LoM Protection System Redundancy
Where noted as ‘Duplicate’, it is a requirement that the Network and LoM protection
systems as listed in Table 5.2 are duplicated in the form of Main and Back-up such
that any single failure of the protection system, including relays, circuit breakers,
power supplies etc will not prevent intended operation of the protection system.
For Inverter connected generators
In a large array of PV, if all inverters are compliant with AS4777, then the on board
systems in the AS4777 compliant Inverters would constitute the Main Protection for
the Common Requirements and No Export or Export requirements. Therefore, the
AS4777 compliant Inverters only require a single overall Back-up Protection, as per
Table 5.1 to meet the requirements of this standard. See Example 1 in Appendix 1.
Synchronous and Asynchronous Generators
Duplicate (Main and Back-up) LoM Protection as per Table 5.2 will be required to be
provided. See Example 2 in Appendix 1.
5.2
Neutral Voltage Displacement (NVD)
Considering the earthing arrangements and the use of delta-star transformer
windings throughout Ausgrid’s distribution network, detection of an 11kV (or other
distribution voltage) network earth-fault on the delta-side of the transformer may be
problematic for generator installations.
While the fault-current contribution from Ausgrid will be interrupted by the opening of
appropriate circuit-breakers, there remains the possibility that a generator may still
energise the faulted distribution network without fault current flowing (due to the loss
of Ausgrid’s earth reference). As such, the generator must not remain connected to
the system if this type of situation arises because of the safety and legal
implications.
The most reliable detection technique for this situation is Neutral Voltage
Displacement (NVD) using voltage transformers connected to the 11kV (or other
distribution voltage) system. Particular attention is needed to ensure that the voltage
transformers (VTs) are of the correct configuration/type for use with this form of
protection.
The installation of NVD will be assessed and negotiated on the merits of the
proposed generator connection point. For generators that have a low-voltage
connection point, it is acknowledged that an 11kV VT connection point may not be
readily available for the customer to provide NVD Protection. In such cases, the
location and responsibility of the installing VTs will be negotiated during the
assessment process. For example, Ausgrid may request NVD be installed and
provide a VT supply to the customer to enable NVD to be implemented.
Settings for NVD are to be negotiated with Ausgrid on a case by case basis.
5.3
Network and LoM Circuit Breaker Fail
The LoM and anti-islanding protection systems must make allowance for circuit
breaker fail (CBF) scenarios in their design.
The form of CBF protection is subject to agreement with Ausgrid, but would
normally require the Main LoM Protection and the Back-up LoM Protection to
trip/open independent circuit breakers/contactors, or by a dedicated CBF protection
scheme.
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For AS4777 Inverter connected generators
The Inverters themselves provide one of the required Circuit Breakers/Contactors.
Therefore the back-up LoM protection, as per table 5.1, is only required to trip a
single Circuit Breaker/Contactor.
For synchronous Generators
It is typical for the main LoM protection and the back-up LoM protection to trip/open
independent Circuit Breakers/Contactors. Alternatively a dedicated CBF scheme
can be provided.
5.4
Over and Under Voltage Protection
Main and Back-up Over Voltage and Under Voltage protection must be provided. All
settings are to be agreed upon by Ausgrid. In the case of Low Voltage AS4777
Inverter Connected Generators, the main protection is that within the Inverter.
Indicative maximum settings for the backup protection are:
LV Connected Over Voltage:
467V phase to phase (270V phase to neutral)
Maximum 2 second operation time
LV Connected Under Voltage:
346V phase to phase (200V phase to neutral)
Maximum 2 second operation time
NB: Main Over Voltage protection settings should be in accordance with the Service
and Installation Rules of New South Wales August 2012, which requires an Over
Voltage setting of 260V. In the case of AS4777 Inverter connected generators, 260V
is the Over Voltage requirements of the Inverter protection.
All other main protection settings are to be at least as sensitive and at least as fast
as the back-up protection settings.
5.5
Over and Under Frequency Protection
Main and Back-up Over frequency and Under frequency protection must be
provided. All settings are to be agreed upon by Ausgrid. In the case of AS4777
Inverter Connected Generators, the main protection is that within the Inverter.
Indicative maximum settings for the backup protection are:
Over Frequency:
Under Frequency:
52Hz
Maximum 2 second operation time
48Hz
Maximum 2 second operation time
Main protection settings are to be at least as sensitive and at least as fast as the
back-up protection settings
5.6
Parallel Operation and Check Synchronisation (CS)
It is of paramount importance that parallel operation does not present a hazard to
Ausgrid staff, public or the customer utilising the generation plant. Consequently, it
is necessary for a failure of supply or irregularity in any of the phases of the Ausgrid
network to which the private generator is connected to result in the complete and
automatic disconnection of the private generator from the Ausgrid network.
The generator cannot connect to Ausgrid’s network unless all phases of the network
are energised in a healthy state. At the switching point to make the parallel
connection between the generator and Ausgrid’s network either synchronisation, or
zero voltage on the generator side of the connection point must be checked before
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allowing closure of the switching point to parallel the generator with Ausgrid’s
network or energise the customers equipment from the switching point. This is of
particular importance at any switching point which can be configured to provide
automatic reconnection of the generator as per Section 5.11.
5.7
Fault Levels and Ausgrid Scheduling
Since existing Ausgrid network and substations were designed and constructed
without consideration for embedded generation, additional sources of supply will
affect the fault-level on the Ausgrid network. As the penetration of embedded
generation continues, a point may be reached where additional sources of supply
will result in the fault-level being greater than the switchgear and equipment rating.
Ausgrid therefore reserves the right to inhibit the output of a generator to ensure
that the system is not compromised under high-fault level or abnormal conditions.
This may be provided via a control signal from Ausgrid such that the generating unit
is either taken off-line (i.e. a ‘soft-trip’) or inhibited from starting up.
Upon assessment of the proposed connection, Ausgrid will advise the customer if
any fault level exist whereby scheduling may be required as part of the installation.
5.8
Loss of Mains (LoM) /Anti-Islanding
The generator must be disconnected whenever the local network is disconnected
from the grid. Anti-islanding devices are required to operate quicker than 1 second
less than the connected feeder automatic reclosing time to a maximum of 4 seconds
(see Sect. 4.10).
There must be two independent LoM Protection schemes, i.e. duplicate schemes
(or Main and Back-up schemes) as per Table 5.1 and 5.2. and Section 5.1
Non-exporting generators:
For generators which are not intended to export power to the Ausgrid network, Grid
Low Forward Power (GLFP) and/or Grid Reverse Power (GRP) Protection is
preferred, however alternate LoM Protection, as per Table 5.1 and 5.2, can be
provided as agreed by Ausgrid. Settings and details of Grid Low Forward/Reverse
Power Protection are to be negotiated with Ausgrid on case by case basis.
NOTE:
Grid Reverse Power Protection is not the same as Generator Reverse
Power Protection.
Exporting generators:
For generators that intend to export power to Ausgrid’s Network, it is preferred for
intertripping to be implemented. Alternatively a combination of Vector Shift (VS) and
ROCOF LoM protection can be provided as per Table 5.1 and 5.2.
All settings are to be agreed upon by Ausgrid.
Indicative maximum settings for the main and backup protection are:
Vector Shift:
8 degrees for strong city/urban networks, up to 12 degrees for weak
rural networks
ROCOF:
1.0 Hz/sec
1 second definite time delay
(Main protection settings are to be at least as sensitive and at least as fast).
NOTE:
Primary testing of the LoM Protection schemes will be required to
confirm the adequacy of the VS and ROCOF settings chosen, this may
result in alteration of settings to be more sensitive in some cases. See
Section 5.
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Ausgrid will be required to approve all Loss of Mains/anti-islanding protection
systems, including which protection trips which circuit breakers to ensure the CBF
requirements of this standard have been met. When the sensitivity of LoM
protection (as per Table 5.1 or 5.2) can not be demonstrated to be adequate, or
where the LoM protection is inappropriate, another form of LoM will be required to
be installed. Any LoM scheme shall be implemented on a three-phase basis to
ensure adequate performance.
Regardless of the type of LoM installed, the generator proponent and customer
must accept that LoM/anti-islanding protection may not be able to be set to
discriminate with other protection systems on the Ausgrid network. Therefore the
generator proponent and customer must accept that the generating units may trip
for system disturbances and fault events both within and external to the local
network that the generator is connected to. This is particularly relevant for Vector
Shift and Rate of Change of Frequency (ROCOF) protection where experience has
shown setting of these schemes to be difficult to avoid nuisance tripping while
providing adequate protection.
It is recommended that proponents design protection and control systems where the
main and backup LoM protection trips circuit breakers/contactors which only control
the generator and do not control other loads within the system. Therefore, any
nuisance tripping as described above will not cause a loss of supply to the
customer, in particular to any critical loads.
5.9
Intertrip Communications Link
If a communication link is installed between the embedded generator and Ausgrid to
facilitate an intertrip or scheduling it must be continuously monitored for integrity. In
the event that the communication link fails then the generator must be automatically
disconnected from Ausgrid’s network until the link is restored. This provides a fail
safe design which requires no back-up LoM type protection.
The provisions of the NER may require some diversity in communication depending
upon the installation.
5.10 Automatic Switching and Reclosing
The majority of Ausgrid feeders are programmed for automatic re-closing after a
period of between 3 seconds and 10 seconds after the successful clearance of a
feeder fault depending on the specific fault location.
Ausgrid Zone Substations are generally fitted with auto-closing to cover for loss of
Zone Transformers and related plant with an automatic restoration time of between
5 and 10 seconds.
Failure of the customer’s equipment to disconnect prior to automatic switching may
result in damage not only to Ausgrid’s equipment but also the generation equipment
unless it is adequately protected.
5.11 Generator Automatic Reconnection
Where the customer has proved automatic reconnection is safe and that generator
state is monitored, then automatic reconnection to the network is permitted. The
device controlling the automatic reconnection must be able to verify normal supply
conditions on the grid for all connected phases (i.e. all three phases for a three
phase connection) for a period of at least 1 minute prior to the device enabling an
automatic reconnection.
Where there are multiple points of automatic reconnection in the installation, each
point must independently be able to monitor and verify normal supply conditions on
the grid for all connected phases for a total period of at least 1 minute before
enabling automatic reconnection of the Generator to Ausgrid’s network.
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In some installations, as will be nominated by Ausgrid, a manual reset may be
required and the generator will not be allowed to be automatically reconnected to
the network. Ausgrid will negotiate the requirements of these proposals on a case
by case basis with the proponent.
5.12 Relay and Tripping Supplies
Unless the requirements outlined in points 1) and 2) below are met, the relay power
supplies, tripping and circuitry associated with the Network and LoM protection
systems must be fail safe. That is any failure of any part of the system must result in
the generator being disconnected and unable to be re-connected to Ausgrid’s
network.
Therefore, circuit breakers with shunt trips will not be acceptable. Where ac (or dc)
supplies are proposed to be used, normally open contactors held in by healthy ac
(or dc) volts or undervoltage release of circuit breakers on loss of ac (or dc) supply,
relay fail and system fail will be required.
Alternate arrangements, usually only associated with HV connections, such as a DC
system utilising shunt trip circuit breakers for the Network and LoM systems may be
accepted with approval by Ausgrid, providing the following 2 points are met.
1) The customer has an approved Installation Safety Management Plan as per
Ausgrid Premises Connection Requirements document ES1.
2) Requirements for the ongoing inspection, maintenance and testing of the
Network and LoM protection systems are defined within the Generator
Connection Agreement applicable to that site.
5.13 Sydney Triplex Network
It should be noted that Sydney CBD Triplex network is different to other parts of the
Ausgrid distribution area and, due to its complexity will impose different restrictions
on the installation of embedded generation.
In particular, there are legacy devices installed at some CBD substations (network
protectors) that may prohibit export. Particular attention will need to be paid to
synchronisation as there are schemes that remotely initiate the opening and closing
of low-voltage circuit-breakers.
5.14 Connection arrangement examples
Examples to illustrate some indicative protection arrangements are provided in
Appendix 1. There are a large number of possible combinations of generation type,
size and connection voltage hence only a representative sample is illustrated.
These examples are for information only, and details may be modified as required
for specific site conditions.
5.15 Relay Requirements
Where applied as per the requirements of this standard, the Network and LoM
relays listed in Appendix 2 are approved for use by Ausgrid.
For Inverter connected generators and Synchronous/Asynchronous connected
generators with a High Voltage Connection Point (11kV and above), at least one of
the required duplicate Network and LoM relays must be compliant with the severity
class (of IEC60255) corresponding to the part of the installation in which it is
located.
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5.16 Approval of Protection Schemes
The following protection drawings must be submitted to Ausgrid for approval:
(a)
A 3 phase ac schematic diagram of protection and control systems
(b)
A DC schematic diagram of all control and protection schemes and
associated logic
(c)
Details of primary and secondary interfaces to the network.
(d)
Details of all protection and metering CTs and VTs and their connections.
(e)
Details of Protection Relay and circuit breakers being proposed
Ausgrid will be required to approve all protection relay settings on the installation
and to witness testing by the customer of LoM protection in additional to normal
AS3000, AS2067 and NSW Service Rules equipment and protection testing by
Ausgrid Installation Inspectors.
Input and outputs of LoM protection relays must be provided with suitable facilities
(e.g. isolating links) to allow testing of the LoM relay to be undertaken without the
need to disconnect and re-terminate wires. Failure to provide these facilities may
cause delays and problems with LoM witness testing.
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COMMISSIONING AND AUSGRID WITNESS
TESTING
Prior to the >30kW connection of the embedded generator to Ausgrid’s network,
Ausgrid will inspect those parts of the generation plant that have a direct effect on
the network. Where necessary, Ausgrid may require specific tests to be carried out
on the generating plant to prove the integrity of the LoM anti-islanding protection
schemes.
The generator proponent must develop in conjunction with Ausgrid to undertake
primary testing of the LoM protection. Details of this plan will depend on the system
arrangement and point of connection of the generator.
As per specific contract conditions, Ausgrid will require notice to be given be given
to allow:

Ausgrid representation during commissioning and all tests that apply to Network
and LoM anti-islanding protection

Access to commissioning test results, test plans, details of test methods and
protection settings

Connection to network during commissioning tests

Ausgrid representation during Primary testing of Loss of Mains protection
including Intertrips, ROCOF, VS and Reverse Power Protection

Testing under and over voltage, frequency etc, generation system protection.
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APPENDIX 1 – SAMPLE PROTECTION
SCHEMES
The following are examples of typical connections which meet the requirements of
this standard. These are examples only. The specific design will be a function of the
customer network and may require different arrangements.
For clarity, only the LoM type protection systems as per this standard are shown.
Short Circuit type protection is not shown.
Legend
NVD
Neutral Voltage Displacement
VS
Vector Shift
UF
Under Frequency
RoCoF
Rate of Change of Frequency
OF
Over Frequency
CS
Check Synchronisation
UV
Under Voltage
GLFP
Grid Low Forward Power
OV
Over Voltage
GRP
Grid Reverse Power
Example 1: >30kW Export Inverter connected at 415V
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Example 2:
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>30kW Export Synchronous Machine connected at 11kV
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Example 3: > 30kW Export Inverter connected at 11kV
Example 4: > 30kW Export Synchronous Machine connected at LV
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Example 5: > 30kW No Export Synchronous Machine connected at 11kV
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APPENDIX 2 – AUSGRID APPROVED
PROTECTION RELAYS
When applied as per the requirements of this standard, the following relays are preapproved to provide protection functions as described in Section 5, Tables 5.1 and
5.2 for Low Voltage connected Generators. Customers may elect to use alternate
relays. All relays used for the generator protection systems must be approved for
use by Ausgrid.
NOTE:
Table A2
Refer to section 5.15 for IEC60255 compliance requirements for High
Voltage connected generator Network and LoM relays.
Manufacturer
Model Identifier
AREVA/Schneider
P923*, P341
Woodward
MFR11
Com Ap
MainsPro
Approved LoM relays for Low Voltage Connection
* Does not provide Vector Surge function, additional relay may be required.
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 Ausgrid.
This document must not be reproduced in whole or
in part or converted to machine readable form or
stored in a computer or imaging system without the
written permission of Ausgrid.
Revision History
Initial issue:
29/08/2008
Last issue:
29/08/2008
This Issue:
01/12/2013
Document Control
Authorised By:
Date: 01/12/2013
Terry Lampard,
Manager – Standards &
Communications
Document Number:
NS194