IEEE Transformer Committee PC57.167 Distribution Transformer - PowerPoint PPT Presentation

IEEE Transformer Committee PC57.167 Distribution Transformer Monitoring - User Mark Scarborough Electrical Engineering Consultant – DuPont January 9, 2019

Transformer Types in DuPont • Control power • Distribution (substation) dry-type • Dry-type in MCCs and control panels • VPI conventional wound and cast coil • 750kVA – 3000kVA • Small dry-type • Distribution (substation) fluid filled • Lighting, receptacle, instrument power panel type • Mineral oil, natural ester, silicone • 5kVA – 330kVA (1 phase and 3 phase) insulation fluids • 750kVA – 5000kVA (some 10MVA and • Specialty 30MVA) • Dry-type and fluid filled for rectifier • Pad-mounted and ASD applications • Mineral oil and natural ester fluids • Pole top • 100kVA – 3000kVA • Small power • Some 20 – 45MVA main substation transformers

Typical Distribution System • Incoming power • Purchased power substations • Mostly all owned by Utilities • 230kV down to 12.47kV • Internal plant distribution • Typically medium voltage (1 – 35kV) but mostly 2.4kV to 13.8KV. Few 34.5kV system. • Utilization • 480V and 575V for most applications • 2.4kV and 4.16kV for motor applications about 250HP and above • 120V / 230V for small loads • Grounding • B-Phase • HGR • LRG • Soild

Transformer Monitoring Techniques • Control power, small dry-type, pole top • Usually don’t do anything. Investigate when something doesn’t work or power goes out. • Some pole tops and small dry-types may get an infrared inspection. • Visual • Probably the most common but questionable as to what people know what to look for. • Some plants require an operator or maintenance technician to walk the main electrical system from substation to substation daily, weekly, or monthly. • Looking for abnormal sounds and or smells, leaks, broken gages, deterioration in paint system. • Infrared Inspection • Typically on an annual basis for most facilities. • Good way to see if cooling system is working or if low fluid level.

Transformer Monitoring Techniques • If transformers are fluid filled, then very good at taking samples for oil screen and DGA on an annual basis. • Typical issues with sample methods and labs and reporting and interpretation. • Need to realize that you have to put some oil back in occasionally. • If critical application, will shut down on a 2 or 4 year interval to do inspection, testing, and cleaning. • Planned shutdowns sometimes are impossible until the system shuts down automatically.

Transformer Monitoring Techniques – Internal Specification • Three (3) internal standards / guidelines • Fluid Filled – 300kVA to 10MVA, 3 Ph, primary voltage 2,400 to 46,000V • Dry-Type – 300 to 7.5MVA, 3 Ph, primary voltage 2,400 to 34,500V • Pad Mount – 2500kVA and below, primary voltage of 34,500V and below and a secondary voltage of 600V and below • Each standard describes the feature sets required on each transformer type. User can add or take away as necessary for their application.

Transformer Monitoring Techniques – Fluid Filled • Optional / Custom • Push to test circuit and/or current • Standard monitoring (4-20mA signal) of space • Field Dial thermometer with alarm heater circuit in ATCs or control box. and control contacts. Space heater control? Thermostat or • Pressure / vacuum gage. no thermostat? • Fan controls and aux contacts off of • Pressure relief valve. fan starter and/or control switch. • Large pressure relief device with • N2 bottle monitoring system with alarm contacts (sometimes alarms. directional shield). • Sudden or fault pressure relay with • Magnetic liquid level gauge with trip and alarm contacts. alarm contacts. • Winding hot-spot temperature indicator relay with alarm contacts. • Add alarm contacts to pressure / vacuum gage. • Infrared view ports on ATC.

Transformer Monitoring Techniques – Dry- Type • Standard • Optional / Custom • Winding temperature with 3- • Push to test circuit and/or current phase hot spot temperature monitoring (4-20mA signal) of indication with peak indicator, space heater circuit in ATCs or contacts for alarm, trip and fan control box. Space heater control? control and fan exerciser. (Typically Thermostat or no thermostat? this is a self contained package • Infrared view ports on ATC. from the vendor.) • Infrared view ports. • Cooling fans w/ running status

Transformer Monitoring Techniques – Pad- Mounted • Optional / Custom • Require that sample valve be • Standard accessible outside of the HV and • Liquid level gauge on 500kVA and LV compartments. above. • Require that all gages be • Dial type thermometer with accessible outside of the HV and “peak” indicator on 500kVA and LV compartments. above. • Infrared view ports on HV and LV • Vacuum / pressure gage on compartments. 500kVA and above. • Alarm contacts on liquid level • Pressure relief device. gage, liquid thermometer, and • Large pressure relief device with vacuum / pressure gages. alarm contacts on 1000kVA and above.

Alarm and Trip Contacts? • In most cases, these transformers are located in an industrial facility and feed a substation or electrical room that has local DCS / PLC (control system) I/O. • Historically, some or all of the alarm contacts would be hard wired to local DCS / PLC I/O cabinets. If it didn’t exist, then it basically didn’t get wired any where. • More recently ……

Alarm and Trip Contacts? • …. we have been using the I/O capabilities on microprocessor based protective relaying and even expansion I/O modules for such devices.

Example #1 • 13.8kV Metal Clad Switchgear • Radial feed to 2500kVA transformer but looped to additional substations. • Switched breaker local to each substation. • Microprocessor relay local to substation not capable of handling I/O from transformer so wired to DCS local I/O.

Construction Interconnection Dwg

Example #2 • 12.47kV Metal Clad Switchgear • Radial feed to 1000kVA substation transformer near by. • SEL-787 protective relay for transformer with differential.

Construction Interconnection Dwg

MV Switchgear Vendor Schematic

Transformer – Vendor Drawing

Example #3

Signals and What Action? • So now we have gotten the signals to the plant DCS or PLC system. • A DCS screen or HMI screen is developed with the alarm points. • DCS / PLC system is monitored by Operation / Operations. Sometimes they don’t know how to respond. • Started developing action / resolution matrix. • Call the on call maintenance electrician? • Go to field and look at the equipment? • System automatically send Text message to on call maintenance electrician response? • Shutdown the process so the transformer can be shutdown? • Alarms can go into a PI Data Historian system but not aware of active trending.

Misc. Topics / Considerations • Confusion as to what to do with an alarm comes in. What action is required? • Firewalls and cyber security. • Not all sites have a centralized DCS or PLC to connect to. • Typically do not monitor of pad mounted transformer but we have some that are in critical applications. • Been some interest in: • On line monitoring for moisture. (On line moisture removal systems in service.) • On line monitoring for DGA monitoring. • Better monitoring of dry-type transformers. Have had some sudden failures. • Starting to experiment with wireless communications technology for instruments. Thinking may be able to use for transformers because not part of process control. • Trending / data collection.

Thank You. • Questions / Discussion