The 132kV transmission line connection to Boggabri Coal Operations was the first of its kind for a coal mine in NSW. It included a 15km transmission line, switching station, and substation to supply the mine's increased power demands of up to 8MVA. While innovative, the project faced challenges integrating the transmission-oriented design with the mine's operations. Collaboration between the transmission and mining industries was needed to address differences in design philosophies, protection schemes, and isolation procedures. Key outcomes included agreements on equipment isolation, communication protocols, and training to safely operate the shared infrastructure.

1. 132kV Connection
A First for N.S.W Coal Mining

2. Introduction
• Where is Boggabri – Situated between Gunnedah and Narrabri in north west
N.S.W approx. 115km West from Tamworth.
• Boggabri Coal Operations commenced mining in 2006
• A significant expansion of site infrastructure was undertaken in 2014/2015
• The 132kV connection was a joint project by Transgrid and Boggabri Coal
Operations.
• Included was 15kM of single structure, double circuit, 132kV transmission line,
132kV switching station and the 132kv/11kV substation.

3. Overview
• Boggabri Coal Operations were an LV customer (HV was
managed by the utility) at inception.
• Site demand was below 2MVA
• An 11kV rural feeder from Boggabri Substation was the
only mine supply source. The service extended over 25kM
(voltage regulation was required).
• Expansion of site infrastructure required power system
demand exceeding the 11kV capability.
• Overall site demand increased to 8MVA (design capacity)
• Local services could not meet the demand – Transmission
was the only option.

4. Why 132kV Connection
?
A first for Mining and Transgrid

5. Network Layout

6. Network Connection
Boggabri Coal
Substation

7. Network Connection

9. Protection Schemes

10. Inter tripping
• 132kV trip signals are duplicated through protection relays from
Boggabri Coal to Transgrid
– Zone Protection (overcurrent, short circuit etc)
– TX Differential
– Emergency stops
– Fire system
– Back up Earth Leakage
– Neutral Earth Resistor failure via NER monitor.
– Transformer Protection (Oil temp, explosion, winding temp, over pressure)
– Arc Fault Detection (11kv Bus)
• Protection devices, Circuit breakers, are in Transgrids Switching Station.
• Faults are cleared by transgrid for all 132kV primary protection or
Intertrip faults

11. Logic Diagram Example

12. Load shed Arrangements
• Transmission systems demand stability
• Transgrid Load shed scheme means exactly what is
sounds like
• 4 Tiers are implemented which shed different load
blocks
• Bus voltage is monitored at the switching station for
trip signal initiations

13. EARTHING
• Common earthing system between Transgrid and Boggabri Coal
• Design requirements - Allowable touch and step voltages were
derived from different standards
• Transgrid – AS2067 ( Calculated)
• Boggabri Coal – AS3007 (step/touch potentials v’s clearance times)
• Transfer voltage levels required separation between
“mine infrastructure area” and the 132kV facility. A
164M exclusion zone has been established for earthed
services entering this zone.

14. EARTHING

15. Challenges
• Design was completed by Transmission orientated Engineers with a different approach to mining
“Risk management base”
• Design review was undertaken by a QLD based engineering company
• Disconnect between project team and the end user of the facility
• System operation – original design philosophy was to run 2 x 10MVA TX’s in parallel which allowed
for a 65kA fault level on the 415V system (terminals of the 3MVA TX supply)
• Fundamental protection schemes, secondary systems, required further development prior to
energistaion.
• HV and LV services crossing operational boundaries. Boggabri Coal and Transgrid share HV and LV
services originating on both sides of the installation.
• Differences in isolation procedures, including hardware between both Transgrid and Boggabri Coal
• Transgrid having a major facility “next door” to the mine substation.
• Unrestricted earth fault levels on the 132kV connection (max 15kA) – transfer voltages
• Reliance of primary protection clearing faults is by the utility – No 132kV protective devices are
owned or operated by Boggabri Coal Operations.

16. Advantages
• Transgrid monitoring
• Transgrid system control monitor the status of Transgrid equipment, including the 132kV circuit breakers,
24/7
• Remote operation of 132kV circuit breakers from Transgrid system control
• Stability of Supply
• The 132kV connection is part of the overall, north west area “Ring Main”. This means the system is very
stable and subject to minimal outages or faults.
• Reduced Arc Flash Categories
• Increased equipment clearances (above 3M) and protection schemes allow for arc
flash categories to be reduced

17. Key Outcomes
• Transgrid and Boggabri Coal Operating agreement implemented
This document identifies
– Equipment isolation instructions, each piece of equipment has an agreed isolation procedure
– Communication protocol’s
– Key contacts for events
– Use and transaction of “High Voltage Equipment Outage” permits.
• Connection Agreement
– Highlights the obligations of each party
– Deals with access and safety scenarios .
– Modifications to the agreed installation and protection settings are dealt with here
• Operational and Maintenance, hazard identification and risk analysis via
consultation with designer, supplier, installer, operator and utility (Transgrid).
– This process expedited the risk mitigation process due to designer information being supplied by key engineers
• Designer based training for operational staff
– Maintenance, Isolation and Operational documents were developed and used as training material
for electrical staff by the designer. Training was delivered onsite.

18. Recommendations
• Where plant and installations are being
constructed, for the purpose of mining
operations, statutory functions should be
involved in the key decisions.
• Collaboration with mining and transmission
industries requires further development.
Mindsets are differing around system
operations and protection functions.

25. Thank You!