Annual transformer liquid sampling
Overview
Over one hundred high-voltage liquid-filled transformers are located across the St. George campus; they act as essential links between the main utility grid and individual buildings’ distribution. The dielectric liquid within the transformers keeps them cool and provides insulation between all live components.
Each of these transformers must be sampled annually in order to analyze their dielectric liquid for various signs of abnormal degradation. This sampling is conducted every August by a third-party contractor with oversight from Facilities & Services technicians.
Sampling process
The majority of campus transformers have external sampling ports, which allows for sampling without shutting down the equipment. Some amount of transformers require an actual shutdown in order to do the sampling
Two samples are taken from the sampling port using clean, uncontaminated plastic receptacles and a syringe.
The technician then carefully documents readouts from the transformer’s gauges for temperature and pressure and records the transformer’s administrative nameplate information onto the samples’ labels.
Samples are then shipped to a laboratory for dissolved gas analysis (DGA) and furan analysis; they are also tested for various liquid properties (colour, visual condition, dielectric breakdown, etc.)
Individualized reports are then produced for each transformer, which are ultimately summarized by the contractor into an action list, as needed.
Provided that results are within tolerances, no further action is required. Should the samples’ values fall outside of normal conditions, transformers will be flagged for additional sampling, careful monitoring, or immediate action. In all cases, F&S staff will be advised of recommended action.
How will buildings be impacted?
During sampling
- The majority of buildings will not be impacted whatsoever; the teams requiring access to transformers will only be accessing utility spaces and not disturb any regular university operations.
- Some buildings have transformers that must be shut down in order to be safely sampled; those buildings will experience an approximately two-hour power outage while sampling takes place. Advance notice of power outages will be communicated via service alert; please subscribe to receive alerts to any relevant buildings here.
- Building occupants may notice uniformed third-party technicians present, as well as F&S electricians, identified by their U of T attire.
Following sampling
- F&S will review the results of the third-party tests to determine next steps, if necessary.
- Should additional sampling be recommended, this will be scheduled within a reasonable timeframe.
- In the event that immediate action is recommended, F&S utilities will begin to take corrective steps as soon as possible, first liaising with the building’s stakeholders (including administrative staff, building engineers, etc). Any remediation work or shutdowns required throughout this process will be communicated in advance via service alert.
Testing standards
We follow the latest standards established by:
- the American Society for Testing and Materials (ASTM)
- the InterNational Electrical Testing Association’s Maintenance Testing Specifications (NETA MTS)
- the Institute of Electrical and Electronics Engineers (IEEE)
Frequently asked questions
This work is generally conducted in the early morning between the hours of 4–8 a.m.
If a power shutdown is required, any equipment using that power will be impacted; the full extent of a building’s shutdown will be clearly communicated via service alert prior to any planned work.
More information
Contact your property manager with any questions regarding annual transformer liquid sampling. Find your property manager here.