As a vital a part of transmission and distribution systems, transformers are built and expected to be unfailingly reliable. Nevertheless, internal faults like partial discharges can occur, and the disadvantage to such faults is that if left un-corrected, they can eventually morph into catastrophic faults that can lead to power outages and even end-user property damage.
Transformer Monitoring: What's Involved
* Data acquisition
* Sensor development
* Data analysis
* Development of links between measurements and failures
Preventing disasters of this nature is actually quite simple, and involves transformer monitoring service. Monitoring transformers and spotting issues before they result in unmanageable incidents can prevent faults usually are costly to fix and may lead to a loss in service. Transformer monitoring mainly involves data acquisition, sensor development, data analysis, and also the development of causal links between measured values and failures of transformers.
Installing monitoring equipment on transformers is generally done for a couple of reasons:
1. Monitoring important transformer functions aid detect developing faults before they end up in a catastrophic failure
2. Monitoring transformer functions can carefully consider a consist of periodic to condition-based maintenance
Monitoring products are permanently that come with the transformer and is online 24/7. Reliable, low-cost monitoring is thus a necessary condition. Failure rates of transformers are generally low (0.2 - 2% per transformer/year), and high-cost failure prevention systems cannot thus be justified, particularly when redundancy is available and the consequential price is thus short amount of. To keep within this cost barrier, some compromise on performance of the monitoring tools is necessary.
Transformer Monitoring: Parameters
* Oil temperature
* Moisture levels
* Operation of cooling fans
* Electrical load levels
In a number of cases, it is plenty to give you a reliable warning signal without online analysis and diagnosis, provided that manual or automatic diagnostic methods are out there to check in the alert. Specifically with regard to power distribution networks in the US,a majority of the transformer population is aging, and the best emerging faults can be thought from the product.Monitoring equipment should thus be designed for field installation on operational transformers might date back an a long time.
Detection of Developing Faults
The main transformer parts that need monitoring are insulation quality, winding temperatures, oil quality, and mechanical moving parts such as on-load tap changers (OLTC). Monitoring the windings and insulation systems for gas-in-oil and partial discharge are crucial; temperature and load monitoring at the other hand, is proved to be base information and in order to included in any type of transformer following.
OLTC failures are typically caused by mechanical faults with bearings, springs, shafts and drive mechanisms, closely followed by electrical faults such as burnt transition resistors, choked contacts, and insulation problems.
Some parameters of transformer monitoring, and also the sensors best applicable are discussed below:
* Dissolved Gas Analysis (DGA)
An established diagnostic method, gas-in-oil analysis involves analyzing the types, concentration and production rates of generated gases. Kinds of of gases are produced based inside the types of faults; for example, overheated cellulose for you to the formation of carbon oxides, but arcing in order to the generation of acetylene.
Depending on the criticality every and every unit, oil samples are taken manually at regular intervals (between 12 and 24 months) and the gasses are extracted from these samples. On-line gas sensors are unquestionably the first choice in designing full time monitoring systems for DGA; simply because the technique of analysis is well established and accepted, and the sensor is frequently capable of detecting an extensive range of failure types and designs.
*Partial Discharges (PD)
Partial discharge testing of de-energized transformers is an invaluable tool for evaluation of overall transformer integrity, however, on-line, real time, partial discharge monitoring is, in general, more expensive and complicated. For example, glass fiber rods acting as wave-guides the actual main tank have been applied to large transformers, but the charge and complexity of installation has made such an unit unsuitable for online monitoring.
There are several advantages together with electrical PD monitoring, even so it has been difficult to create field applications thanks into the difficulties in separating bodily and mental PD sources. Sensors that think you are tested and developed currently include externally fitted acoustical sensors, may more cost-effective but are susceptible to disturbances from rough outdoor substation areas.
The load capability from a transformer is restricted by the spot of your windings. The hot spot is often calculated indirectly from measurements of oil temperatures and load current. An alternative method involves fiber-optic temperature sensors that are installed in the winding within manufacturing function. These sensors may be two varieties - fibers which study the temperature at a single point, and distributed fibers that measure the temperature along their length of time. All of these systems involve high costs; in particular, the distributed fiber sensor is the most expensive for install and can even only be used to new transformers.
The condition of the insulation can be judged using parameters as well, with regard to example moisture levels and particulate content. Data interpretation when you use parameters isn't straightforward, but new techniques are being developed using software to examine the large body of historical data available and identify patterns of progression towards inability. If similar deterioration is detected regarding your transformer in service, remedial action could be taken.
Other regarding online sensors have ended up investigated. Involving such systems are online measurements in the moisture content of the oil, static charge in oil, optical sensors and pump monitor. Also on-line measurements among the moisture your cellulose by optical fiber techniques are being studied. In general, strategies do not have a strong coupling to important and frequent failure modes.