Solving ambient temperature issues around transformer operations at a Coal Mine, Queensland.
Background:
The North Goonyella mine was experiencing an airflow issue with its mobile transformer that was causing high ambient temperatures. It was imperative that the site comply with minimum airflow requirements for underground operations, so they approached us to design a custom transformer that would keep this temperature down.
Peabody needed us to meet specific guidelines for the project, which were as follows:
- The equipment in the longwall gate road cut-throughs had to be ventilated by a maximum of 0.1 m3/sec.
- The enclosures needed to be able to adequately dissipate the heat generated by components contained within the enclosures or busway chambers and other external heat sources at an ambient temperature of 30°C.
- Where assisted cooling was required, liquid cooling was preferred.
From a technical perspective, the substation and pump station electronic components and cable ratings had to withstand the rated temperature.
Solution:
We developed a unique transformer cooling concept that involved combining a low-pressure coolant circuit with an external heat exchanger. The design allowed coolant to run through the coolant chambers on the lid and the longer sids of the transformer. The external heat exchanger cooled the hot coolant using mining water.
The design considerations were based around:
- General purpose/fire mine water (including quality, temperature, pressure and longwall demand)
- Cooling capacity of the system
- Effect of the system on the mine water
- Transformer Ex p protection
- Group I Zone 1/ERZ1.
Other considerations included:
- Rating for the system pressure
- Poor heat transfer through the welded pipe
- Coolant for heat transfer
- Handling the water flow without too much pressure loss
- Concern regarding pipe leaks, stress cracking and corrosion.
Outcome:
The development of the Gas Natural Coolant Forced (GNCF) transformer assembly was successful, resulting in the required airflow with cooling in place. In addition, testing revealed:
- At the end of the heat rise test, the coolant tank wall/lid temperatures were less than 6°C above the incoming water temperature.
- The difference in water temperature from input to output was 4°C.
- The shut down/loss of power test showed coolant chamber walls increased to a maximum of 80°C before trending downwards.
