Toronto WWTP HVC Upgrade Design 

Project Requirements

Power Control Engineers were engaged for the contestable ASP3 design services relating to the Toronto WWTP HV power upgrade; including associated electrical reticulation works. The site was required to be upgraded to a new HV supply, consisting of a single Ausgrid HVC installation with a “RMICB” supply arrangement. In addition, existing OH line clearance was required to be rectified due to non-compliance with current Network Standards (NS220).

PCE ASP3 Deliverables included:

• Certified Design Package; and
• Summary Environment Report.

Task

Toronto WWTP completed minor restoration/upgrade work during a previous High Voltage Upgrade completed in 2014, at which time Ausgrid indicated that any future contestable works to the electrical apparatus at Toronto would necessitate the following upgrades:

• The High Voltage Connections would need to be brought up to modern standards;
• Ausgrid and the client would require separate switching HV installations. Currently the RMU is operated by both Ausgrid and the client; and
• Requirement of appropriate Service Protection Device. 

In addition, there were other issues related to operation and safety:

• No remote switching available; and
• Overhead line clearance from ground is not to correct standard and creates a hazard for delivery trucks at site.

Design

The design addressed the network standards non-compliance by establishing a new location for a HVC Unit at the site frontage. The location was met with several issues:

1. NSW SiR requires a MSB to be located within 30m of the Point of Common Coupling. The negotiation with Ausgrid included a report detailing the protection results for a non-standard installation. The report was issued to Ausgrid installation inspectors for review which resulted in approval for our design in favour of the client.

2. To address the existing OH clearance non-compliance all existing poles within the site required decommissioning. At the end of the line by decommissioning the mains (CCT180) the final pole (HV-61359) was no longer structurally compliant which was required to be replaced and upgraded. Through negotiating with Ausgrid compliance, the option to install a stay was approved, allowing the pole to remain and reduce the costs to the customer.

3. To finally establish a loop (N-1 contingency) for switch B, the HVC was designed to interconnect to the existing OH HV network. The point of interconnection was rejected by Ausgrid initially. A solution was proposed to UGOH at the next pole which was met with rejection also. Both cases Ausgrid argued the existing OH mains angle was not able to have a UGOH construction and a 2-5 construction would not allow for a UGOH construction, in addition mid-span clashing was flagged due to the OH construction 2-1 to 2-5. The resolution was negotiated by demonstrating if we changed the 2-5 construction to a 2-1 construction the mains would operate within the allowable separation clearances.

4. The proposed HVC location required some vegetation removal. The issue was raised with Ausgrid who requested an ecology assessment to be completed. The report was a lengthy process however, demonstrated the impact was acceptable and covered all impacts related to vegetation clearing from the kiosk unit, to the entry and exit points of the under bore. 

Summary

PCE was able to overcome each challenge presented to deliver the HVC design and associated SER in the agreed timeframe. Construction has been quoted and proposed to be commence in Q2, 2021. We are in continuing liaison to address RFI’s and queries related to the project to ensure the construction phase is completed efficiently.