Rotor Pole Temperature Sensor Network Danu, Justin, Jay

Project Description Noxon, Mt Noxon Dam, Mt is used to compensate for the power generated by wind. This along with imbalances in the air-gap of the generators leads to heating of the pole faces on the rotor. Noxon, Mt

Specifications Interface to PLC: 4-20mA Accuracy of +/-5 C Sample Rate: ~2 per minute Self-powered Insulation Class F: 155C max There are many sensors to monitor the generators for preventative maintenance and reliability but there is no rotor pole temperature sensor system to measure pole temp. The purpose of the project is to create a sensor system to measure the rotor pole temperature. The data will be used in worst case analysis and protection of the rotor insulation. 5 Units, 4 sisters (1-4): 72 poles, unit 5: 68 poles

Rotor Pole Hot Spots No Damper Windings Air-gap Imbalance Location of hot spots is likely on the pole face due to slot harmonics and air-gap imbalance. The actual hot spot location is unknown. Our focus is a proof of concept such that the sensor location can be determined at a later time.

Temperature Sensing Remote: from Stator Direct: on Rotor Track Rotor Position Not accurate Direct: on Rotor Very accurate Sensor Options Communication Channel Power? Can’t use current and voltage measurements of the field since the windings are in series. This would result in a calculation for the average temperature of the coils.

Block Diagram

Temp Sensor RTD Thermocouple RTD: platinum temperature dependent resistor ~$55 Thermocouple: voltage output proportional to thermal gradient of different metals IR: Analog outputs

RTD ~$33 Flat Package Fast Response Tight Tolerances

Thermocouple Easy to Customize -50 to 200 C 2.2C Accuracy

Communication Wireless Magnetic Optical Zigbee Wired Power Line Carrier Channel requirements: 30bps per pole 2.16kpbs per rotor One of the challenges faces by the team is getting the temperature readings of the rotor to the programmable logic controller. Originally, the team opted to use infrared technology and place a sensor on the stator. The pole temperature would be taken remotely as each pole passed by the sensor. Unfortunately, this technology already exists and Avista has a beta version installed on one unit at Noxon. The Beta version does not work well so Avista opted for a solution with the sensor mounted on the rotor. Therefore, the design must implement a communication channel. Four different technologies are under consideration.

Zigbee ~$20 per 250kbps 915Mhz or 2.4Ghz Digital interface 65,000 nodes

Optical ~$15 per channel 115kbps IR channel Digital interface Short Range (<1m) Rotor tracking required

Magnetic Custom Design Drive, receiver, protocol, error detection/correction Unsure of Bandwidth Very sensitive Short range Rotor tracking required

Power Line Carrier ~$50 and up per channel 1.44kbps half duplex Slip Ring Channel Filter networks

Power Rotor Field winding Wind Magnetic field Vibration Solar Receiver 120Vac

Field Winding Full load: 500V @ 1200A Series connected ~7V per pole

Magnetic Field DC Field w.r.t. Rotor Slot Harmonics External magnets

Vibration Piezoelectric Resonance Low power IEEE documents as well as datasheets show power output on the order of uW to few mW for vibrations on the order of 1m/s^2 Online documents for vibrations on rotors show accelerations on the order of 0.1m/s^2, thereforee this option does not seem like a good route

Wind speed ~ distance from shaft Rotor ~100rpm rotor 30’ radius Wind speed ~ distance from shaft Wind Rotor ~100rpm rotor 30’ radius Wind speed ~ distance from shaft

Solar Independent of Generator Operation Stable Output Cons Retrofit Wiring Length

Power supply Design

Proposed Solutions Block Option 1 Option 2 Option 3 Power Magnetic Field (slot harmonics) Magnetic Field (permanent magnets) Solar Comm. Ziqbee Optical or Zigbee Zigbee Sensor RTD

Option 1 Pros Communication reliability Cons Winding in air-gap Cost Independent modules Cons Winding in air-gap Cost ~$20 x2 Zigbee ~$100 RTD (3-pack) ~$25 power supply ~$25 external hardware

Option 2 Pros Power supply = Tracking Cons More complex comm. Cost ~same as option 1

Option 3 Pros Comm. Reliability Constant Power Cons Wiring Cost ~$120 more than option 1

Test Plan Stationary Accuracy Synchronous Generator Functionality Need a temp probe as reference Difficulty in testing slot harmonic magnetic field (especially on smaller machines)

Timeline