Lauri Kumpulainen

The Smart Solution for the Prediction of Slowly Developing Electrical Faults in MV Switchgear Using Partial Discharge Measurements

An electrical fault in switchgear results in interruption of power supply, damage to equipment, and poses a hazard to personnel. This paper focuses on the detection of slowly developing faults leading to internal arc, using online monitoring technologies in medium-voltage switchgear. Unconventional radio-frequency (RF) techniques for discharge measurement are highly attractive but have not been widely applied in the industry due to their ineligibility to quantify actual discharge. On the basis of various benefits, a new application of a differential electric field ( D-dot) sensor for partial-discharge (PD) measurements has been introduced in this paper. The reliability of the sensor has been confirmed through comparison with a commercial high- frequency current transformer. An attempt has been made to quantify the apparent charge of online PD measurements. The energy of signal captured by the D-dot sensor has been compared with the apparent charge quantity calculated from current pulse measured by the conventional method. A second degree polynomial relation exists between the cumulative energy and apparent charge. It has been shown that when apparent charge is plotted against the cumulative energy of the RF signal for a number of pulses, defects can be separated on the basis of cluster positions within the scatter plot.

Reducing Arc Flash Incident Energy Level in an Offshore Gas Production Unit Using Intelligent Electronic Devices—A Case Study

This paper evaluates the protection system of an offshore gas production unit and proposes utilization of devices dedicated to identify the arc flash incidents inside the panels. A quantitative analysis has been performed by comparing the incident energy levels of the original design with the levels provided by the new design. The new design includes numerical relays equipped with dual sensing of arc flash: optical detection of the light and high-speed overcurrent detection. The analysis indicates that a drastic reduction of incident energy can be achieved. The reduction is based on very fast detection and elimination of the arc, lowering the arcing time.

Signal processing of PD measurements to predict arcing faults in MV switchgears

Arcing faults in MV switchgear cause serious hazard to personnel, significant damage to equipment, and often serious process interruptions. Many of the faults develop slowly, e.g. because of insulation degradation or loose connection. An interesting research question is whether these developing faults could be detected before they escalate into devastating high-power faults. Detection of partial discharges (PD) or monitoring of temperature has been suggested in on-line monitoring systems. In this research, a switchgear panel has been subjected to PD in the laboratory and measurements have been captured by different sensors and recorded by high frequency oscilloscope. Generally, the on-line signals are suppressed by high frequency noise, therefore, the de-noising of PD measurement is of paramount importance to get reliable arcing fault prediction results. The discrete wavelet transform (DWT) to de-noise such PD signals has been employed in this paper. Time domain and frequency domain comparisons of original and de-noised PD signal reveal the significance of this technique for arcing fault prediction in medium voltage (MV) switchgears.

Maximizing protection by minimizing arcing times in medium voltage systems

Arcing faults in the forest product industries are real risks that often lead to severe injuries and fires. From an economic point of view, the consequences due to direct and indirect costs can be extremely high as well. There are various opportunities to prevent arcing faults, but faults cannot be totally eliminated. This is why several approaches to mitigate the consequences of arcing faults have been introduced, particularly in the last decade. Several manufacturers have started to produce arc-flash protection relays based on optical detection of light energy from an arc event. In most applications, the light information is confirmed by overcurrent information before a trip command is initiated to an upstream current-breaking device. The tripping of a circuit breaker, for instance, occurs in only a few milliseconds. In most cases, this seems to be the state-of-the-art technology leading to very reasonable incident energy levels. However, it is essential to be able to minimize not only the thermal impact but also the pressure wave. This paper investigates technology aimed at maximizing the protection for the pressure wave.

Protection at the speed of light: Arc-flash protection combining arc flash sensing and arc-resistant technologies

One of the most critical aspects of reducing both personnel injury and equipment damage is through the reduction of the energy available to an arcing fault. The initiation of a trip and the clearing time (opening) of any upstream device is a critical component in the reduction of the resultant arc flash incident energy. Combining technologies that detect and interrogate both arc flash and the associated arc current signatures in combination with arc resistant switchgear or controlgear, can provide a coordinated solution for controlling the level of incident energy at various points within the distribution network. Hybrid systems of this type provide the highest level of personnel protection, along with comprehensive equipment protection, as detection and initiation of tripping is implemented faster than with conventional relaying techniques alone. The reduction of the overall trip time can reduce equipment collateral damage, reconditioning time and lost productivity resulting from downtime. These types of coordinated systems will also lower the personal protective equipment (PPE) requirements based on incident energy. This paper compares several systems including conventional overcurrent protection, zone selective and various light and current sensing systems.

Protecting at the speed of light: Combining arc flash sensing and arc-resistant technologies

One of the most critical aspects of reducing both personnel injury and equipment damage is through the reduction of the energy available to an arcing fault. The initiation of a trip and the clearing time (opening) of any upstream device is a critical component in the reduction of the resultant arc flash incident energy. Combining technologies that detect and interrogate both arc flash and the associated arc current signatures in combination with arc resistant switchgear or controlgear, can provide a coordinated solution for controlling the level of incident energy at various points within the distribution network of a forest product facility. Hybrid systems of this type provide the highest level of personnel protection, along with comprehensive equipment protection. Detection and initiation of tripping is implemented faster than with conventional relaying techniques alone. The reduction of the overall trip time can reduce equipment collateral damage, reconditioning time and lost productivity resulting from downtime. These types of coordinated systems will also lower the personal protective equipment (PPE) requirements based on incident energy. This paper compares several systems including conventional overcurrent protection, zone selective interlocking and various light and current sensing systems.

New pre-emptive arc fault detection techniques in medium voltage switchgear and motor controls

For Forest Products based industries, the significant benefits of pre-emptive arc-flash protection and online condition monitoring of electrical equipment are not well known. This paper provides a summary the research surrounding the development and testing of new advanced sensor technologies for this purpose. More extensive and detailed measurements, regarding significant defects leading to an arc flash event, have been completed since the first portion of the research was completed [1]. Early detection of impending faults and the prediction of future arc-flash occurrences in medium voltage (MV) switchgear and motor control centers (MCC) can be very beneficial. The development of new sensor technologies, both for partial discharge (PD) measurement and thermal detection, are discussed and evaluated. The two most common non-contact causes leading to an arc-flash event in MV switchgear and MCC are insulation degradation and thermal stresses. This paper will highlight very detailed results measured under both of these conditions in the laboratory and actual installed conditions. An effective signal processing method, used for extracting the essential indication data and the integration of this system into an existing protection PLC or SCADA, are outlined.