| ELECTRICAL INNOVATION AT JENOLAN
BILL RITCHIE and ERNIE HOLLAND
In our opinion there are four major factors involved in the electrification of caves, they are:- 1. Position of electrical fittings;
To Address Each Situation 1. Position of electrical fittings If fittings are away from accepted pathways through the caves then persons servicing such fittings must be aware of the correct approach and need for care to be taken. If all fittings are at pathway points then they become both subject to visitor interference and possible visual pollution. 2. Environmental Factors The major considerations here are whether the fittings e.g., cables, are visible or hidden. In being visible, the damage could be to the aesthetics and in being buried or covered the risk would be of a physical nature upon the environment. Each and every section of the cave has to be assessed to the minimum impact on the cave and visitor. 3. Visitor Enjoyment This covers what the visitor expects, whilst realising different visitors expect different things. Lighting must show what the environment represents:- geology;
an entertaining and adventurous factor. 4. Who does it We emphasise that this point was the major consideration - who does it. In our opinion the ideal committee to light caves would be a speleologist, electrician and cave guide, but who has ever seen the ideal committee. Here at Jenolan we have what we would consider the correct component in that the person now doing the cave lighting is a speleologist of many years experience, an electrician by trade, and a cave guide, also for many years standing. We will now outline the electrical history of Jenolan, the problems associated with electrical standards applying to caves or the lack of them, the modern innovations and methods that we are implementing the correct (we hope) procedure taking the above points into consideration. Jenolan - A Unique Electrical Area History - Jenolan Firsts First cave lighting in the world, 1880, nine months after Edison invented the electric light globe. Permanent lighting installed 1884-1887 Imperial Cave, 1892 Lucas Cave. The first power source was a 6 hp vertical steam generator located in the Grand Arch. Fuel requirements and smoke from the fire presented quite a problem which was solved when a large electrical capacity water wheel was installed in the Blue Lake area, another first. The “Leffel Wheel” was subsequently moved further downstream to take advantage of a greater head of water to power a second dynamo. Additional load in the form of new caves required additional generating capacity. A pair of British Westinghouse hydro-generators, purchased during the First World War, were installed at the present hydro station with a rating of 20 kva each and requiring to be manually balanced in operation, hence the need for the cottage just above the hydro station to be occupied by the electrician of the day. An interesting sidelight to these generators is that they were the second pair to leave England, the first were lost at sea when the ship on which they were cargo was sunk during the First World War. The load continued to exceed the generating capacity so a diesel generator located in a building known as the “diesel house” was installed and run only weekends or other peak periods to satisfy demand. Incidentally the building is still known as the ‘diesel house’, although the diesel has long gone. In the early fifties Jenolan was connected to the State grid as it existed at that time through Southern Mitchell County Council. Those who remember the fifties will recall the notorious blackouts, load shedding, and criticism of Mr Conde who had the unenviable job of improving the State’s generating capacity. In this atmosphere, Jenolan, which had always been self- sufficient electrically, found its new source of supply unreliable to say the least. As a temporary measure a second diesel generator was installed at the present Baal/Orient entrance to supply the western side of the Grand Arch. Plans were in train for the supply and installation of a larger 71 kva hydro plant to replace both diesels and both smaller hydros. This was completed in 1957 and is in service today although it only feeds six of the nine show caves, the sewerage treatment works and eight staff cottages. Whilst the hydros have always generated at 2.2 kv the voltage within the caves has always been controlled to 110 v, and since the Leffel Wheel, alternating current. Late 1984 a diesel generator of 175 kva was installed in the old boiler house and plans are in train to duplicate this generator in the same building. The continual increase in our generating capacity in addition to the supply available from Southern Mitchell, highlights the ever-increasing electrical load at Jenolan. The caves alone represent a total load of 200 kw. The wiring within the caves has also been through several up-grades, the original wiring consisted of BRI cables on porcelain insulators and know as open wiring. Some of the wiring although 100 years old and not connected to the supply, still exists in its original form today. Knife switches controlled the circuits, an interesting time was undoubtedly had by all the guides. The open wiring was replaced around the 1920s to 30s by lead cables fixed to the cave wall and floor and still with knife switches. In the mid-fifties rubber insulated, plastic sheathed cables replaced most of the lead cables, new switch-boards with leabah panels, metal surrounds and some 130 surface mounted tumbler switches were fitted. Usually double insulation was the order of the day, earthing was shunned so that with electrical isolation of the supply through transformers, double insulation, no earth, it was considered shock proof. Every electrician since and some guides would contest that assertion. Almost all switch-boards were fitted with socket outlets, two way circuits predominated and many wires resulted. Protection in the form of fuses were installed in the mains feeding a cave or section of cave. No protection was provided for the sub-circuits. We considered this to be unacceptable and began inquiries to determine how this situation came to be. Cave electrical systems appear to be something no one wanted to know about, it was considered low voltage, yet, anything over 32 v AC is lethal. It was our own supply. Council was not involved. The Public Works Department were involved when it was decided to re-wire the Jubilee Cave. They, in a series of letters to the Standards Association of Australia (SAA) proposed a system, with eventual SAA approval, which exists today at Jenolan, Wombeyan and Abercrombie. The system comprised a single phase centre tap transformer, two wire primary, both actives, two wire secondary at 55 v each, 110 v across the lamps, and the centre tap earthed. Fuse protection was in the mains only, with no sub-circuit protection; it was considered desirable to allow sections of sub-circuit wiring to burn out rather than have sections of cave in darkness. The joints were made in the sub-circuit cable prior to each lampholder. Switchboards were to be as previously described, double insulation to be maintained, no earths. Against this background, maintenance was increasing within the caves. Gravel pathways were being replaced with concrete, platforms were cemented and enlarged, new handrails were installed. Cave cleaning was commenced, originally with steam then water. Power was required for equipment such as cement mixers, electric drills, electric water cleaning equipment. Tingles and shocks resulted and it soon became apparent that the old system was totally inadequate. Contact was made the supply authority, Southern Mitchell County Council, then the SAA, the Energy Authority of NSW, and the Public Works Department. No positive advice was available, all references led us back to the letters of 1957. As Jenolan is probably the largest show cave system in Australia with some 8.6 km of lit passageway, it was apparent that we were on our own with the job of designing a system suitable for cave conditions. Our criteria consisted of the following:- 1. Electrical safety against shock for both public and
staff, remembering an annual visitation of
250,000
We have developed a system which incorporates all of the above and have wired sections of cave to this standard, although the communication and emergency lighting facilities are yet to become operational. Cave supply transformers are of a standard configuration, three phase
where load requires it, with standard actives and neutral, secondary
at 110 v. Mains are protected by circuit breakers with each
cave individually controlled. Sub-circuits are protected by individual
circuit breakers at each point of origin, tapped joints in the sub-circuit
cables are eliminated by a loop in and loop out system at each lampholder
The middle module on each board has been fitted with a DIN rail or mounting which can accommodate up to three circuit breakers and is labelled accordingly. Active and neutral links are fitted within the board each of which can accommodate mains termination and sub-circuit origination. Another module is provided as a standard 110 v configuration power outlet. We have found these boards extremely versatile. A type of MEN earthed system has been employed with the aim of establishing an equipotential earth value in the cave. To achieve this we are installing earth electrodes at every second switch-board following the electrical run. A continuous earth wire linking each switch-board, the neutral link and the earth electrode eliminates return voltage in the neutral cable, which has been measured at 12 v in a 110 v system. All exposed metal, hand rails, bridges, ladders are all connected to the earth system to avoid the leakage and tingles which have been common in most cave systems. We have been requested by the SAA to record and advise them of our methods as they have indicated that a code, or at least a paper, is to be prepared on wiring in limestone caves with the system we are employing as the basis of that code. In that regard, although challenging, we have found this work very satisfying. |