Protection device simulation

Dr. A. Shaw at the University of Maryland Eastern Shore in Princess Anne, Maryland, is evaluating textile substrate for pesticide barrier effectiveness and comfort. Tests will be conducted to assess effectiveness of decontamination processes for these personal protection devices. Diazinon emulsifiable concentrates will be used to contaminate fabrics. Simulated wear studies will be conducted in the laboratory to assess the efficacy of these fabrics in protecting human health. 

The distribution line, the pole, and the home appliances in the house shown in Figure 6.16 can be represented by horizontal and vertical distribution line models and lumped parameter circuits [27,28]. The grounding electrodes of the pole, the telephone line SPD, and the home appliances, if grounded, are modeled by a combination of a distributed line and a lumped parameter circuit to simulate the transient characteristic [29]. However, this section adopts a simple resistance model with a resistance value taken from the experiments discussed in References 29 and 30, as the vertical grounding electrode used for a home appliance is short and the transient period is much shorter in the phenomenon investigated in this chapter. A protection device (PD) is installed in a home appliance, and the NTT SPD is represented by a time-controlled switch prepared in the EMTP [31]. 

It, however, requires a further improvement of the overall simulation method to achieve a quantitative agreement with a measured result. For example, a surge protecting device has to be carefully represented based on its circuit and the nonlinear characteristic. Also, a grounding impedance should be modeled considering its transient characteristic rather than a simple resistance adopted in this section. 

With these data, one can determine the dielectric curve the machine must have when switched with such an interrupting device. This can be compared with the actual dielectric curve of the machine (Figure 17.18) obtained from its manufacturer to decide the compatibility of the interrupting device for the machine or vice versa and the extent of surge protection, if necessary. For more details and results of similar simulation tests, see Central Board of Irrigation and Power (1995). 

The nail penetration test is very important and is considered to simulate an internal short in a cell. No electronic device can protect against an internal short, so the cell... 

However, the European normalization committee is in the process of looking at the issue and is working on the EN-13648-1 Cryogenic vessels -Safety devices for protection against excessive pressure - Part 1 Safety valves for cryogenic service. The tendency is to go to a much more reliable test as described hereafter which will simulate the real process conditions to a greater degree. 

Where circuits are protected by an RCD we must carry out a test to ensure that the device will operate very quickly under fault conditions and within the time limits set by the lET Regulations. The instrument must, therefore, simulate a fault and measure the time taken for the RCD to operate. The instrument is, therefore, calibrated to give a reading measured in milliseconds to an in-service accuracy of 10%. 

Simulant vapors released into the test chamber are stirred with fans to produce a uniform challenge. The feed is monitored with proper analytical devices and data acquisition system. This system has been employed to generate a high volume of vapor in a large chamber for testing the protection efficiency of unhardened collective protection shelters. These shelters typically use filtered air to overpressurize the inside of the shelter to preclude infiltration of unwanted vapors. 

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