IEEE Transformer Committee PC Distribution Transformer Monitoring - User

Transcription

1 IEEE Transformer Committee PC Distribution Transformer Monitoring - User Mark Scarborough Electrical Engineering Consultant DuPont January 9, 2019

2 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

3 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

4 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.

5 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.

6 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.

7 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.

8 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.

9 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.

10 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

11 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.

12 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.

13 Construction Interconnection Dwg

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

15 Construction Interconnection Dwg

16 MV Switchgear Vendor Schematic

17 Transformer Vendor Drawing

18 Example #3

19 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.

20 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.

21 Thank You. Questions / Discussion