IEEE Transformer Committee PC57.167 Distribution...
Transcript of IEEE Transformer Committee PC57.167 Distribution...
IEEE Transformer Committee PC57.167 Distribution
Transformer Monitoring - User Mark Scarborough
Electrical Engineering Consultant – DuPont
January 9, 2019
Transformer Types in DuPont
• Control power • Dry-type in MCCs and control panels
• Small dry-type • Lighting, receptacle, instrument
power panel type • 5kVA – 330kVA (1 phase and 3 phase)
• Specialty • Dry-type and fluid filled for rectifier
and ASD applications
• Pole top • Small power
• Some 20 – 45MVA main substation transformers
• Distribution (substation) dry-type • VPI conventional wound and cast coil • 750kVA – 3000kVA
• Distribution (substation) fluid filled • Mineral oil, natural ester, silicone
insulation fluids • 750kVA – 5000kVA (some 10MVA and
30MVA)
• Pad-mounted • Mineral oil and natural ester fluids • 100kVA – 3000kVA
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 • Standard
• Field Dial thermometer with alarm and control contacts.
• Pressure / vacuum gage. • Pressure relief valve. • Large pressure relief device with
alarm contacts (sometimes directional shield).
• Magnetic liquid level gauge with alarm contacts.
• Optional / Custom • Push to test circuit and/or current
monitoring (4-20mA signal) of space heater circuit in ATCs or control box. Space heater control? Thermostat or no thermostat?
• Fan controls and aux contacts off of fan starter and/or control switch.
• N2 bottle monitoring system with alarms.
• Sudden or fault pressure relay with trip and 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
• Winding temperature with 3-phase hot spot temperature indication with peak indicator, contacts for alarm, trip and fan control and fan exerciser. (Typically this is a self contained package from the vendor.)
• Infrared view ports.
• Cooling fans w/ running status
• Optional / Custom • Push to test circuit and/or current
monitoring (4-20mA signal) of space heater circuit in ATCs or control box. Space heater control? Thermostat or no thermostat?
• Infrared view ports on ATC.
Transformer Monitoring Techniques – Pad- Mounted • Standard
• Liquid level gauge on 500kVA and above.
• Dial type thermometer with “peak” indicator on 500kVA and above.
• Vacuum / pressure gage on 500kVA and above.
• Pressure relief device.
• Large pressure relief device with alarm contacts on 1000kVA and above.
• Optional / Custom • Require that sample valve be
accessible outside of the HV and LV compartments.
• Require that all gages be accessible outside of the HV and LV compartments.
• Infrared view ports on HV and LV compartments.
• Alarm contacts on liquid level gage, liquid thermometer, and vacuum / pressure gages.
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