ANALISIS PARTIAL DISCHARGE DAN PREDIKSI USIA LAYAK ISOLASI BELITAN STATOR GENERATOR

ABSTRACT 
The arise of partial discharge in isolation of the winding stator generator is thing that general because existence ageing and excessive stress. Partial discharge in isolation of the winding stator occur in the core slot area or endwinding area. The problem that occur in isolation of the winding stator generator is the presence of corona and high partial discharge in the endwinding area caused by ineffective monitoring of partial discharge. This research discusses about that occurrence corona and partial discharge, and the effectiveness of repairing insulation of the stator winding that performed during overhaul. The analysis methods used is comparative, characteristics and trending, and linear regression to predict the age of operation worthiness in isolation of the winding stator. The results of the analysis showed that, the cause of corona and high partial discharge due to damage to the isolation surface consequence contamination from bearing seal oil which have seepage and load & thermal cycling, with the age of operation worthiness shortest isolation of the winding stator during ± 2 years 1 month 21 days or only increased 14 days after overhaul. 
  
Keywords : partial discharge, corona, linear regression, age of worthiness isolation of the winding 
  
  
ABSTRAK 
Timbulnya partial discharge pada isolasi belitan stator generator merupakan hal yang umum terjadi karena adanya penuaan dan tekanan yang berlebih. Partial discharge pada isolasi belitan stator terjadi di area slot inti atau area endwinding. Permasalahan yang terjadi pada isolasi belitan stator generator adalah adanya korona dan partial discharge tinggi pada area endwinding yang disebabkan karena kurang efektifnya monitoring terhadap partial discharge. Penelitian ini membahas tentang terjadinya korona dan partial discharge, serta efektifitas perbaikan isolasi belitan stator generator yang dilakukan saat overhaul. Metode analisa yang digunakan adalah komparasi, karateristik dan trending, serta regresi linear untuk memprediksi usia kelayakan operasi isolasi belitan stator. Hasil analisa menunjukkan bahwa, penyebab terjadinya korona dan partial discharge tinggi karena adanya kerusakan pada permukaan isolasi akibat kontaminasi minyak dari seal oil bearing 5 yang mengalami rembesan dan load & thermal cycling, dengan usia kelayakan operasi tersingkat isolasi belitan stator selama ± 2 tahun 1 bulan 21 hari atau hanya mengalami kenaikan 14 hari setelah overhaul. 
  
Kata kunci : partial discharge, korona, regresi linear, usia layak isolasi belitan


Development Of Iris Power Partial Discharge Monitoring
The development of Iris Power partial discharge testing instruments in 1990's was funded by the North American utility industry (CEA and EPRI) to provide machine owners a method of detecting stator insulation problems and obtaining adequate data to make maintenance decisions independent of equipment manufacturers.
The TGA-B was designed specifically for monitoring partial discharges under normal electrical, mechanical and thermal machine operating stresses without interference from external noise such as power system corona, output bus arcing or other common electrical disturbances.
There are now over 65,000 Iris Power partial discharge Epoxy Mica Capacitive Sensors installed across thousands of motors, generators and metal glad switchgear globally that are monitored by Iris Power portable and continuous instruments.

Data Collection Method
The online partial discharge test takes less than 30 minutes per machine with data collected in a simple, safe and non-destructive manner based on sound principles that are recommended by manufacturers and industry standards such as IEEE Std. 1434-2014 and IEC60034-27-2: 2012.
The operator connects low voltage coaxial cable from the Iris Power TGA-B portable instrument to a coupler termination box. The TGA-B instrument is then connected to a control computer that runs the PDLight Pro and PDView software using a USB or Ethernet cable.
The test is initiated through the PDLight Pro software which automatically collects the partial discharge data while the machine is running and without any interference to normal operation of the generator.

Sensor Installation and Configuration
Iris Power Epoxy Mica Capacitors (EMCs) are 80pF capacitors that are used to block high voltage output from the generator since impedance is inversely proportional to frequency. The 60 Hz or 50 Hz power frequency is filtered with >30 MΩ impedance while the high frequency partial discharge pulses up to 250 MHz easily pass through the EMC with only 10's Ω impedance. This allows us to see small partial discharge pulses of under 100 mV on rotating machines rated over 3.3kV.
Iris Power typically installs two 80pF epoxy mica capacitive couplers per phase on generators. Noise pulses originating outside the machine arrive at the sensor closer to the power system first. Partial discharge pulses originating in the machine winding arrive at the sensor nearest the machine first. This allows the TGA-B to automatically distinguish between noise and winding partial discharge based onpulse arrival time.
Motors with over 30m of cable the switchgear may require only one epoxy mica capacitor per phase. The TGA-B automatically analyzes the pulse shapes to separate distorted pulses originating from the power system from machine partial discharges.

Data Analysis and Information Outputs
Iris Power is foremost focused on providing a clear, reliable and repeatable result that allows the user to understand the true condition of the motor or generator and to make educated decisions on operations and maintenance. The TGA-B instrument has been designed to automatically collect partial discharge data and output the relevant information needed to provide a decisive means of:

Machine Partial Discharge
Electrical disturbances including partial discharges in the transmission lines (corona) or transformer as well as sparking of overhead cranes or on-site welding can create pulses similar to partial discharges. It is important to be able to understand the difference between power system noise and machine partial discharges to avoid false positive indications, to prevent unnecessary shut-downs and to avoid in-service failures.
The Iris Power TGA-B is designed specifically for Turbine Generators and Motors to ensure machine partial discharges are viewed and analyzed separately from system noises.

Separation of System Noise
Installation of two couplers per phase allows the TGA-B instrument to automatically distinguish between power system noise by evaluating pulse shape and the time of arrival of pulses.
Pulses originating outside the generator which arrive to the instrument through sensor closest to the system so can be automatically separated and classified as disturbances.
The pulses that arrive at the machine side sensor are automatically classified as machine partial discharges. Any pulses between the two sensors are automatically classified as pulses on the isolated phase bus.