it be opened by mistake or otherwise, the plant within would be immediately shut down and earthed. Circumventing all these safety precautions, a junior attendant got over the fence by means of a ladder and received a fatal shock. A short distance within the fence there was a connector plug for attaching a portable lamp for use in cleaning the apparatus when not at work. It appeared that he entered the enclosure in order to connect a radiator at his desk outside the fence to the lighting socket within it.

Two fatal accidents occurred in the testing departments of electrical manufacturing works. One was due mainly to carelessness in the non-observance of the routine rules of the works, and the other to lack of the most elementary precautions.

Three fatalities were due to the omission of, or inefficient, earthing of motors or starting gear. In one case, in a saw mill, a motor and saw were mounted on the same iron bed plate. The "earthing" was by the holding down bolts in the concrete foundation. The supply was from a substation on the premises, 440 volts, 3 phase, the neutral point not being earthed. It was realized that something was wrong with the plant, as when switched on sparks were observed at a part of the conduit. One of the men took hold of the hand-wheel of the saw and was killed. Subsequent tests showed that the saw and motor, etc., were live at 440 volts, there being also an earth fault on another phase of the supply. At the inquest the electrician stated that he was "self-taught " and knew of no other method of earthing than by foundation bolts. In the next case the responsible electrician was a highly skilled man. There had been some trouble with the starting up of a motor (440 volts 3 phase), and a new starter had been connected up as an experiment. As it was only on trial that electrician had not thought it necessary to connect it to earth. Unfortunately it developed a fault and the motor stopped. An apprentice electrician who went to investigate was killed by a shock from the starter. The fatality was particularly tragic as the apprentice proved to be the son of the responsible electrician. In the third case, in a large thread mill, where the power supply is 500 volts, 3 phase, earthing of the electrical plant was effected through the heavy gauge screwed conduit protecting the wires, a method which is very commonly relied upon, and is in general satisfactory. A girl of 16 had charge of two spinning frames, each driven by a 5 H.P. motor attached to the frame. One frame was running and the other was standing. She was engaged in cleaning the latter, and was kneeling on the floor to reach the lower parts. She had no shoes or stockings on and her feet were in contact with the running machine when she received a fatal shock. It subsequently transpired that a fault had occurred on the motor of the running frame which had become charged up. The earth connection through the screwed conduit was found to have been broken at a joint which had parted owing to vibration and not having been properly screwed up in the first instance. Examination of the

installation, which otherwise was of a high class order, did not disclose any other such defect. Since the accident the firm have put in a separate copper earthing system throughout the works. The electrical continuity of the tubing appears to have been tested when the installation was first put in. The accident therefore emphasises the necessity for proper testing of the continuity of such conduit, both after erection and at subsequent intervals. The method of "testing" earth connections by means of a Megger" or other instrument intended for measuring very high resistances or insulation, as is often done, is, of course, quite useless. In this case the firm in question have devised a special testing set for the purpose, using a small accumulator giving an appreciable current, so that reliable results can be obtained.

The use of unearthed portable apparatus, as usual, caused several accidents, including some fatal cases. These accidents are attributable to the ignorance of the requirements of the Regulations as to earthing, or to deliberate inattention thereto by persons who, having neglected the precautions without accident perhaps a number of times, fail entirely to realise that they may do so once too often. In some cases a contributory cause lies with the indifference of the makers of the apparatus in not providing ready facilities for earthing. Thus, portable electric drills and other tools are made up and sold with a few feet of twin flexible wire terminating in an adapter for connecting to an ordinary lamp-holder, instead of with a 3-wire flexible, the third wire being for earthing, terminating in a 3-pin earthing plug. The absence of any recognised standard for 3-pin plugs also may have some bearing on the matter. A fatal accident occurred in the basement of a boiler house of an important municipal generating station. Work was being done in a steel flue for forced draught requiring the use of an electric drill. Three-pin plug connectors with earth connections were provided on the wall near-by for the very purpose of connecting such apparatus. The drill was, however, provided only with a twinflexible and an adapter. Connection was therefore made to the circuit without using the earthing arrangement provided, or any other in lieu thereof. Although a fault in the drill was at once indicated by the fuse blowing with the drill resting on the metal floor of the flue, it did not serve to convey any warning of danger to the men or to the electrician who was called to examine the drill. It was then placed on a wooden box and the fuse replaced and was found to work all right. Two men standing on the earthed metal flue then proceeded to lift it. Both received severe shocks, one being killed.

Two further fatalities were investigated in which electric drills were concerned. In each case a man was actually using an electric drill when he collapsed and died. The drills were connected by "adapters " in lampholder and were not earthed. As no actual fault or leakage could be found with the apparatus

i

definitely to prove electric shock, an open verdict was given at the inquest in one case and "natural causes "in the other. These cases are not included in the table of fatalities.

As usual, several serious shock accidents occurred to persons using ordinary metal lampholders on flexible wires as portable lamps, in one case with a fatal result.

In my previous reports I have repeatedly drawn attention to the danger of shock from alternating current at low pressure, i.e., not exceeding 250 volts, such as is delivered to consumers' premises from public supply mains, a danger which is still not generally realized even by electrical engineers. Most of the fatalities have been from circuits at 200 to 250 volts, this being the range of the usual supply systems. Although the actual pressure received by the victim may have been considerably less in some cases, it has not been definitely ascertainable. During the year under review there were five (as against twelve the year before) fatal cases. One of these was of particular interest in showing that a very low pressure may be dangerous if the conditions are specially favourable to good contact. It is often asked what pressure may be regarded as absolutely safe. The answer depends entirely upon the conditions of contact assumed. In the case in question the pressure of the circuit could not have exceeded 64 volts and was probably only about 55 volts. It occurred at a power house where, during the coal strike, persons had been stealing coal from the outside coal store. In order to try to stop these depredations a fence had been erected round the coal heap consisting of a copper wire on porcelain insulators. The intention was to electrify the fence and thereby give any intruder trying to pass it a mild electric shock, just sufficient to scare him from going further. The fence was tested after completion by persons putting their hands on it, and it was found to give only a mild tingling effect. Unfortunately later on a fatal accident occurred. A youth of 18, who was found within the enclosure, was being chased away, and on arriving at the fence he slipped and fell on to a sheet of corrugated iron, at the same time grasping the wire fence. The weather was very wet, the ground was wet, and the youth's clothes and hands were wet. The result was that he was unable to let go the wire. One of the engineers who was close by tried to release his grasp of the wire but failed to do so and ran to switch off the current. The duration of the shock was from one to two minutes. Had the ground been dry doubtless no such accident would have occurred. As I have mentioned in former reports, one of the chief contributory causes to low-pressure alternating fatalities is the fact that at pressures above about 40 volts with alternating current a person grasping a live conductor and getting a shock through his body may be unable to release himself, a condition which clearly existed in this case.

In previous reports I have referred to the fact that there is a very narrow line between a trivial and a serious electric shock. In the course of a year many people receive electric shocks of

(27385)

D

varying degree without any serious consequences. Some cases, however, come very near to being fatal, but by reason of the fact that the victim is not kept away from work for a period of over three days are not reportable. A few are, however, reported, or otherwise come to the knowledge of the Department. Amongst those investigated last year, and not included in the table of accidents, one occurred in a municipal power station, where an electrical fitter received a 6,600-volt shock, and was rendered insensible. He was brought round by artificial respiration and returned to work in two days. In a similar case in the testing department of a cable works an attendant received a shock at several thousand volts, but was only away from work for one day. In another municipal station a man was rendered unconscious by a shock at 220 volts, but returned to work within three days.

They also

The Divisional Electrical Inspectors have been very fully occupied in their respective areas, and their reports contain many items of interest. Each of them refers to one aspect of the greatly increased size of generating stations, and of the units of plant therein. Generating sets of 20,000 K.V.A. are becoming common and still larger sizes are being installed in some cases. Large stations are being interconnected. These developments result in enormous increase in the possible short-circuit capacity. This affects particularly the problem of sub-station switchgear. Much of the existing switchgear which has hitherto been adequate will no longer be so, and unless a very extensive replacement takes place failures will inevitably occur. Examples of the destructive energy of short circuits whereby switchgear is destroyed and in a few cases the sub-station demolished have occurred. refer to the large increase in the number of sub-stations, particularly of the smaller class and those of the kiosk type of which many do not come within the scope of the Factory Acts. In the case of the larger sub-stations generally improved design and construction was noted. In some of the smaller examples also the design has been well thought out, both in regard to continuity of supply and to safety of attendants. The desire for cheapness in respect of keeping down capital cost has, however, in some cases been carried to such an extent as to necessitate, in the event of any work having to be undertaken on any of the high-pressure apparatus, the shutting down of the supply over extensive areas involving all the sub-stations supplied from the same high-tension feeder, a condition which may be admissible for a time in newly developing areas of supply, but which may speedily become intolerable as the load and number of consumers increase, and it is apt to lead to risks being run by the attendants in order to avoid such interruptions in the supply. In some cases it has led to noncompliance with the Regulations and very dangerous conditions in respect of the attendant. It has, however, been demonstrated in many such cases that the necessary provision for safety would have added little, if anything, to the cost, if it had been properly considered in the original design. Fortunately in many cases

designs are submitted by the manufacturers or the engineers of the supply undertakings to the electrical inspectors before being proceeded with, and mistakes are obviated.

The standardisation of small sub-stations and transforming stations of the kiosk type would probably be of service in respect of reduction in cost. At present there are probably more different

designs than there are electrical undertakings.

Mr. McColgan (Northern Area) reports in the case of one undertaking, where small consumers in a rural district are so scattered about that the expense of a low-tension distributing main would not be warranted, that a 3,000-volt feeder is tapped where required and a transformer is directly connected without any switch or fuse gear, the transformer being regarded as part of the hightension distributor. A transformer fault is then, of course, equivalent to a cable fault. So far no additional trouble appears to have been experienced with this arrangement, and if small transformers can be made as reliable as cable there would seem to be no special objection to the method.

Mr. Brown (Midland Area), amongst other matters, deals with improvements in switchgear, but gives instances of cases where in new switchgear mistakes have been made, which seriously affect it from the point of view of operation or maintenance, necessitating in certain events either an entire shutdown of the plant or the taking of undue risks by the attendant. Thus in the case of the main switchboard in a high-tension generating station, potential transformers are provided only for the generators, and together with their fuses are placed in the generator oil switch cell, where they are only safely accessible when the machine is shut down. If one generator only should be running and the potential transformer fuse should blow, it is impossible, in the absence of an independent bus-bar potential transformer, to synchronise a second generator, and a complete interruption of the supply must occur during the change over.

Precautions observed as a matter of course in the case of indoor switchgear are often neglected in the case of open-air switchgear; thus fuses are placed in positions dangerous of access by reason of adjacent high-tension conductors. Similar mistakes occurred with medium pressure switchgear. Thus in a new artificial silk mill where the process is essentially continuous, the switchboard was arranged with four oil switches cramped together on each panel without any sub-division, making it impossible to carry out even a small adjustment without shutting down the whole supply.

In the Southern Area there appear to be more works using electricity in industrial processes than in other parts of the country. Mr. Swann has consequently to devote a considerable portion of his time to these processes, which it is frequently found are very dangerous as originally installed, but are capable of being

(27385)

D2