Končar TMS - Bushing monitoring

Transcription

1 Končar TMS - Bushing monitoring Many recent studies have shown that bushing failure is one of the most common causes of transformer failure. Thus need for bushing diagnostic and monitoring system has risen. Although, the offline diagnostic gives more accurate and precise insight in bushing insulation state, it is still not common practice for substation maintenance to perform such test very often. Main reason is that it demands transformer outage, well trained personnel and expensive equipment. Koncar TMS bushing monitoring provides insight in bushing insulation state while transformer is online. Developing fault inside bushing now can be detected in very early stage so proper action can be taken to save substation equipment and personnel. Powerful digital signal processor module enables precise measurement of bushing leakage current amplitude and phase angle. By measuring those parameters, relative dissipation factor change ( tan ) and relative capacitance change ( CC0 ) can be estimated. Key features: Bushing capacitance and tanδ monitoring High speed analog input channels Synchronous acquisition Digital signal processing Bushing adapters for various tap design Voltage RMS, Peak measurement Overvoltage detection Frequency and phase measurements

2 Koncar Electrical Engineering Institute Inc. System Architecture: Končar bushing monitoring system is modular system and comes in two versions. Basic system for 3 bushings On-line bushing capacitance and tanδ monitoring for 3 bushings (6 optional) Overvoltage detection Advanced algorithms and analysis tools Built-in additional 8 analog inputs for measuring load current, temperature, humidity, etc. Built-in additional 2 digital outputs for alarm signaling Expandable system up to 6 additional modules On-line bushing capacitance and tanδ monitoring for 3 bushings (optional up to 12 bushings) Overvoltage detection Advanced algorithms and analysis tools Built-in additional 8 analog inputs for measuring load current, temperature, humidity, etc. Built-in additional 2 digital outputs for alarm signaling Expandable system - analog input, analog output, digital input, digital output or RTD module can be added to create complete transformer monitoring system

3 Measurements methods: Končar Bushing monitoring can monitor bushings using 3 methods. Each method has its advantages and disadvantages. Method selection has to be based on measurement requirements, available conditions in substation and budget. Sum-of-phasors Advantages: Simple method Less cabling High sensitivity Disadvantages: Advantages: Network unbalance problems Bushing to Bushing comparison No network unbalance problems Monitors 6 bushings Disadvantages: More cabling Available only if 2 transformers are operating concurrently on same busbar Voltage transformer reference Advantages: Absolute measurement No network unbalance problems Disadvantages: More cabling VTs are usually placed far away from transformer and very often not available

4 How it works: Measuring path of the bushing monitoring system is shown on the figure below. Signal is coupled from test tap of bushing by tap adapter and measuring impedance. Measuring path provides safe connection to the earth, thus preventing appearance of dangerous voltage at the test tap. Several levels of voltage limiting devices are built-in test tap adapter, measuring impedance and TMS cubicle. TAP ADAPTERS Further, signal is connected to DSP (digital signal processor) which measures amplitude and phase angles related to the signals from other bushings or secondary terminal of voltage transformer. In sum-of-phasors method, resultant phasor is calculated from signals of 3 bushings. Changes in capacitance and tan are then calculated from resultant phasor. This technique provides very good sensitivity to changes of tan because relatively small changes in resistive component of leakage current cause big changes in resultant phasor. Bushing-to-bushing comparison method is used for monitoring of 6 bushings for 2 transformers that are operating concurrently on same busbar. While each set of bushing can be monitored independently using sum-of-phasors method, this method gives more information by comparing signals from pair of bushings that are operating on same lineto-earth voltage. Changes in bushing capacitance and tan are calculated from changes in phase angle and amplitudes ratio of leakage currents. If signal from secondary of voltage transformer is available, absolute value of capacitance and tan can be measured by definition. This method provides best results, but often it is not possible to use it because there are no available VTs in substation or they are too far from transformer.

5 Additionally, Koncar Bushing Monitoring can detect peak value of fast overvoltage (including 1.2/50 µs wave) that appears during switching of transformer or atmospheric discharges. During overvoltage event, very fast comparator detects that voltage is out of bounds and activates state-of-the-art peak detector circuit which samples the peak value of overvoltage. Both, positive and negative, peak values of overvoltage can be measured. Typical signal waveform is given below: This information is of great importance because insulation of transformer and bushing can be damaged during those events.

6 Technical specifications: Basic system 3 bushings General Power consumption 25 W Transient overvoltage protection up to 50 V Power supply interruption protection 5 ms Communication protocols: IEC , MODBUS/TCP Power requirements Power supply range Power consumption Physical characteristic Dimensions (HxWxD) Weight V 40 W 150x277x171 mm 1.5 kg Temperature range Operating temperature range -40 to +85 C (IEC 60571:2006, Class Tx) Storage temperature range -40 to +85 C Shock and vibration IEC 61373:2010, Category 1, Class B Electromagnetic compatibility This product meets requirements of the following standards: EN50155:2007 EN :2006 EN :2007 EN :2005 Digital outputs Number of channels 2 Relay type DPDT Min. switching load 100 ma at 12 V Maximum switching capacity AC 1 A at 250 VAC 1 A up to 50 V 0.4 A at 120 V Analog Input Module Number of channels 8 AD resolution 12 bits Frequency range Hz Update rate, all channels 1 ms Input type configurable current or voltage Current 0 30 ma Voltage ±30V Bushing voltage transducer Number of channels 3 Input voltage Vpp Monitored quantities Relative Capacitance change resolution 0.1% Dissipation Factor change resolution 0.05%

7 Technical specifications: Expandable system General Power consumption 25 W Transient overvoltage protection up to 50 V Power supply interruption protection 5 ms Communication protocols: IEC , MODBUS/TCP Power requirements Power supply range Power consumption Physical characteristic Dimensions (HxWxD) Weight V 50 W 150x439x171 mm 3 kg Temperature range Operating temperature range -40 to +85 C (IEC 60571:2006, Class Tx) Storage temperature range -40 to +85 C Shock and vibration IEC 61373:2010, Category 1, Class B Electromagnetic compatibility This product meets requirements of the following standards: EN50155:2007 EN :2006 EN :2007 EN :2005 Digital outputs Number of channels 2 Relay type DPDT Min. switching load 100 ma at 12 V Maximum switching capacity AC 1 A at 250 VAC 1 A up to 50 V 0.4 A at 120 V Analog Input Module Number of channels 8 AD resolution 12 bits Frequency range Hz Update rate, all channels 1 ms Input type configurable current or voltage Current 0 30 ma Voltage ±30V Digital Input Module Number of channels 32 Input range 0-30 V Input current 2.9 ma at 30 V Transient overvoltage 2500 V RMS Digital Output Module Number of channels 8 Relay Type SPDT Maximum switching capacity AC 1 A at 250 VAC 1 A up to 50 V 0.4 A at 120 V RTD module Number of channels 8 Type 4 wire RTD AD resolution 16 bits Update rate, all channels 0.56 s Excitation current 2 ma Data type Temperature ( C) or Resistance (Ω) Monitored quantities Relative Capacitance change resolution 0.1% Dissipation Factor change resolution 0.05%

8 Drawings: Basic system 3 bushings Expandable system with up to 8 additional modules