Ground Fault Interrupter

接地断路器

Ground fault interrupters are designed to protect from electrical shock by interrupting a household circuit when there is a difference in the currents in the "hot" and neutral wires. Such a difference indicates that an abnormal diversion of current from the "hot" wire is occurring. Such a current might be flowing in the ground wire, such as a leakage current from a motor or from capacitors. More importantly, that current diversion may be occurring because a person has come into contact with the "hot" wire and is being shocked. When a circuit is functioning normally, all the return current from an appliance flows through the neutral wire, so the presence of a difference between "hot" and neutral currents represents a malfunction which in some circumstances could produce a dangerous or even lethal shock hazard.

接地保护装置设计用于通过中断家庭电路来防止电击。当“火线”和中性线中的电流存在差异时，这类装置会中断电路。这种差异表明电流可能异常地从“火线”分流，例如可能通过地线流动，如电机或电容器的漏电流。更重要的是，这种电流分流可能是因为有人接触了“火线”而被电击。当电路正常工作时，所有电器的回流电流都通过中性线流动，因此“火线”和中性线电流之间的差异表示一种故障，这种故障在某些情况下可能导致危险甚至致命的电击隐患。

GFI's are required by the electrical code for receptacles in bathrooms, some kitchen receptacles, some outside receptacles, and receptacles near swimming pools. The horror story scenarios which led to these code requirements are things like dropping a hair dryer or a portable radio into a bathtub with a person, causing electrocution. A typical circuit breaker interrupts the ciruit at 20 amperes, but it takes only about 100 milliamperes to electrocute a person in such a scenario. The GFI is designed to detect currents of a few milliamperes and trip a breaker at the receptacle or at the breaker panel to remove the shock hazard.

根据电气代码，浴室内的一些插座、厨房的一些插座、一些外部插座以及靠近游泳池的插座都需要安装GFI。导致这些代码要求的恐怖故事场景包括将吹风机或便携式收音机掉入浴缸中，而有人在场，从而导致触电。典型的电路断路器在20安培时会中断电路，但仅需约100毫安的电流就足以在这样的场景中电击人。GFI的设计是检测几毫安的电流，并在插座或断路器面板上触发断路器，以消除触电危险。

The GFI has a "Test" button which causes a small difference between "hot" and neutral currents to test the device. In an example given by John de Armond, the test button put the 120 volt supply across a 14.75 K resistor, producing a current of 8.2 mA. The UL requirement for a GFI is that it trip when there is 5 mA of leakage current. There is also a reset button to use after it has been tripped.

GFI有一个“测试”按钮，它会使“火线”和“零线”电流之间产生微小差异以测试设备。如约翰·德·阿隆德给出的例子，测试按钮将120伏的电源加在14.75千欧的电阻上，产生8.2毫安的电流。UL对GFI的要求是当有5毫安的漏电流时，它会触发断开。此外，还有一个复位按钮，在断开后可以使用。

Thanks to John de Armond for clarifying the operation of the GFI

感谢John de Armond澄清GFI的操作