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
• 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
• n 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