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Extinguishing Fires of Live Electric Equipment

As it is laid down in general professional standards, fires of live equipment are to be extinguished only after de-energization. But as the saying goes, it’s the exception that makes the rule, and this also applies to continuous plant technologies where an outage can cause significant economic losses. Representing the plant-based Fire Service of Paks Nuclear Power Plant Zrt., Fire & Rescue Head Mr. István Schreiner and Training Executive Mr. József Tóbi demonstrated the conditions for such an exemption at a disaster prevention conference held in Sopron.

Fire & Rescue Head Mr. István Schreiner addressed the conference as follows ‘Rules defined by experts of the plant-based Fire Service of Paks Nuclear Power Plant (ATÜ) and VEIKI-VNL Villamos Nagylaboratóriumok Kft. are applicable to extinguishing fires of live low-voltage (50 to 100 V) and high-voltage (1000 to 6000 V) electric networks and equipment on the site of Paks Nuclear Power Plant Zrt. using water in cases where disconnection from the mains cannot be carried out or rapid intervention can save human lives or prevent significant damage to property or disaster from occurring.’

The project launched in 2002 to work out and lay down standard procedures for extinguishing fires of live equipment was implemented in the following cycle. As a result of the project, documentation containing the rules of extinguishing fires of live equipment has been prepared. It is laid down in the documentation that such fire extinguishing activities are considered as work done in the vicinity of dangerous high voltages. In such cases, the physical contact with live parts (or parts deemed to be live) or access to them within arcing distance is prevented by work procedures accomplished with the greatest possible care and precaution, and not by the use of some kind of technical means (Hungarian Standard no. MSZ 1585:2001).

The rule of human factor is of utmost importance during such activities as extinguishing fires of live equipment may exclusively be carried out by persons in full possession of all the necessary knowledge and skills, properly trained for work-related hazards and exposures as well as relevant labour safety regulations who have successfully passed a first aid exam. Special theoretical preparatory and practical training means and facilities are available to help employees acquire the necessary skills to pass an exam. In addition to the careful building of human resources, the company should take great care to ensure that proper technical and organizational conditions are available on a continuous basis. Without entering into details of the relevant standards and qualification documents, some measures, intended to increase the level of safety while extinguishing fires of live equipment, were introduced at the conference.

Parameters of the protective gloves used for extinguishing fires of live equipment should comply with the voltage level of the electric equipment under extinguishing operations. All protective gloves (26 kV) should be checked by visual inspection for marks of any damage and tested for air-tightness before use. When fighting fires of live mains and electric equipment, each person who carries out either preliminary inspections or actual intervention should have with him an appropriate rod rated for 40 kV that is suitable for separating persons or objects who/which may have entered a live circuit.

Before starting fire-fighting activities on live mains or equipment, the head of fire-fighting operations should arrange for the motor ambulance to be called out. The ambulance crew should be properly trained in applying effective, efficient and successful methods for the treatment of the physiological effects of, and responses to, an electric shock and well-equipped with mans and appliances suitable for providing first aid in the vicinity of live mains and electric equipment. The use of jet pipes on fire engines other than those certified for fighting fires of live equipment is strictly prohibited to prevent the application of any inadequate means. Only firemen who have been thoroughly trained for such work and have participated in periodical theoretical and practical training may carry out operations to quench fires of live equipment with water. The lecturer answered the question on how to proceed when someone accidentally enters a live circuit, and on what factors would influence the effects of an electric shock and what to do in order to diminish such effects. What will influence the amperage conveyed by an electric shock? (Italics indicate points that MAN can do for.)

Dimensions of the contact surface (DO NOT wear watch, necklace or other body jewels while working => they increase the contact surface!) Route of the current flow inside the human body. (The more severe the effects of an electric shock may be the more vital organs such as lungs, heart, etc. are affected.) Condition and humidity of the skin. Duration of the electric shock. (Parts of the body also have their specific resistance, which will, however, cease to exist in 1 to 5 seconds.) Frequency of the current. (Frequencies between 15 and 100 Hz are dangerous, or even lethal, while frequencies over 100 kHz are harmless, as ions of the human body cannot accommodate high-frequency oscillations.) Unexpectedness of the electric shock. State of mind. Influence of alcohol.

Training executive József Tóbi focussed his thoughts on the outcomes of the cable fire that occurred in the Nuclear Power Plant in 2001 and showed that immediate intervention may be necessary at places not equipped with built-in fire extinguishers. The Nuclear Power Plant has equipment with uninterruptible power supply, therefore, in case of fires, they cannot be de-energized, yet fire-fighting operations should start as soon as possible in order avoid any major damage to property. And, add to that, access distances cannot be more than a few metres. One should know that voltages of 230 V, 400 V and 6 kV are used in plant buildings and 15 kV leaves the turbine room to reach the transformers. 120 and 400 kV are the typical outdoor voltages throughout the site. Let’s see some reasons for why we had to regulate fighting fires of live equipment so exactly:

– Following from the technology applied, the vital and uninterruptedly supplied consumers cannot be de-energized;
– Occurrence of disaster situations can be prevented (through the use of technologies strictly regulated and defined by experts);
– Fire-fighting started in an early stage of a fire event can save lives.;
– Unpredictable human and technical factors (tapping, uninterruptible multiway power supply); and
– Clarification of the relevant legal background.

Experiments are aimed at
– selecting ideal means for fire fighting; – establishing appropriate fire-fighting technologies (safety distances and applied jet pattern) for max. 6 kV equipment;
– applying foam for fighting fires of live equipment;
– testing protection capabilities of the personal protective equipment (gloves, protective clothing, boots) used; and
– ensuring that appropriate opportunities for preparing and training the staff are available.

The test methods were prepared and finalized on the site of VEIKI VNL Villamos Nagylaboratóriumok Kft., Budapest, between March and October 2002 and in April 2003. The starting point for the work was the testing of manual fire extinguishers for fire-fighting parameters. In order to obtain exact measurement results, all means were subjected to so-called disturbance tests before setting about to the actual measurements. The measurements were carried out on the basis of examination of fighting fires of live equipment as defined in Hungarian Standard no. MSZ EN 3 (Requirements for Manual Fire Extinguishers): Acid-proof steel plate connected to 15 kV voltage.

A computerized measuring system with a detector attached to the jet pipe was applied to measure creep currents flowing via the extinguishing jet between the plate and the jet pipe for a period of 20 seconds. In order to obtain precise results, conductivity of the utility water available in both Paks and Budapest was also tested. Therefore, firemen used their own syringes and water since iron content of the water of Paks is much higher than that of the utility water of Budapest. Test designers took care in carrying out measurements under rainy weather conditions as such conditions can easily occur in the real life. Measurements in rain were also accomplished at standard distances, i.e. from 3, 6 and 10 m, with distance allocated jet patterns. It could be stated on the results available that rainy weather conditions did not affect in any manner fire-fighting operations applied in the event of live equipment. 7 jet pipes were tested and the results obtained were put down on record. Only personal protective equipment, i.e. protective gloves, boots and clothing, in standard use at fire brigades were used for testing purposes without revealing any problems with them. Rubber gloves proved to provide an increased level of safety during tests.

Personal preparation was found to be the neuralgic point of intervention as much depends on how people involved in fire-fighting operations behave, not to mention the physiological effects of electricity, compliance with the relevant regulations and circumstances of work near live equipment. All in all, results of experiments started in 2002 were a significant contribution to the issue of Decree no. 19/2007 ÖTM, which contains provisions as to safety regulations to be complied with during intervention in nuclear facilities and equipment. According to the provisions of the Decree, the Fire Service of Paks Nuclear Power Plant Zrt. has the right to carry out fire-fighting operations on live equipment. Cable cutting for equipment and wires, which are not known to be energized and how to de-energize can be a next step in a prospective test series. Further issues on the long-range are the proper fire-fighting technologies applicable for high voltage equipment and 120 and 400 kV systems, application of various fire-fighting substances, improvement of personal and auxiliary protective equipment, selecting the best fire-fighting solutions and technologies and, on such a basis, updating Fire and Technical Rescue Regulations.

Florián exPress