Mounting current transformers

Two types of phase/current sample pickup elements are commonly used the sample loop and torroidal current transformer (TCT). The sample loop consists of a single turn unshielded loop of rigid construction, with a fixed gap at the open end for connection of the sample line. The device must be mounted on the tower near the point of maximum current. The loop can be used on towers of both uniform and nonuniform cross-section. It must operate at tower potential, except for towers of less than 130 electrical degrees height, where the loop can be operated at ground potential. 

Current transformers can be mounted on the stator terminals outside the generator casing. The transformers can he delivered in accordance with the purchaser s requirements. 

Two (2) to six (6) separate service entrance cables connected to the secondary side of one utility owned transformer can connect to separate main circuit breakers or main load brake fused disconnect switches that are mounted next to each other. The sum of the ampacity of all of the service entrance conductors must have a current rating equal to or greater than the present and future maximum demand for the plant. This approach can reduce the cost of the service entrance installation but will not provide the additional level of protection provided by having one main circuit breaker or one main fused disconnect switch. Therefore it is not as reliable. 

Contact detectors are somewhat easier to miniaturize. There are generally two subtypes those with twin axially mounted electrodes and those with twin or quadruple radially mounted electrodes. The former can be operated in DC mode or AC mode. In the DC mode, the detector signal directly originates from the field strength between the electrodes and, given the current, is inversely proportional to the detector cell resistance. In the AC mode, both axially and radially mounted electrodes form part of a closed primary circuit of an isolation transformer, the output of which is also inversely proportional to the cell conductivity. Alternatively, the output can be linearized with respect to the conductivity. 

Iradiations above room temperature are carried out by pressing the powder into a 6 X 1 mm. slot milled in a 5 mm. diameter aluminum rod. The rod replaces the normal bit in a 25W soldering iron which acts as a heat source. The assembly is mounted vertically with a thermocouple fixed in the sample holder. Temperatures can be controlled to within 5°C. by regulating the current through the heating element with a Variac transformer. 

A schematic of the COPO facility is shown in Fig. 1. The basic idea is to simulate a corium pool on the lower head of a WER-440 reactor with a two-dimensional slice of it in a linear scale 1 2. The 10 cm wide slice is bounded by two parallei polycarbonate plates. The height of the pool can be adjusted with the maximum of 80 cm. At the top, the facility spans 1.77 m. The simulant fluid is water, with some zinc sulfate added in order to adjust the electric conductivity for Joule heating. For the heating AC current is conducted through seven pairs of electrodes mounted on the surface of the polycarbonate walls. The maximum voltage used in the experiments is 30 V and the maximum power attainable, from the transformer currently in use, is 6 kW. The polycarbonate walls are covered with thick thermal insulation with peek holes for laser doppler (LDA) measurements. The facility is typically operated at maximum temperature of about 80 C. 

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