Editing Ground loop (electricity) (section)

== Description ==
A ground loop is caused by the interconnection of electrical devices that results in multiple paths to ground, thereby forming closed conductive loops through the ground connections. A common example is two electrical devices each connected to a [[mains power]] outlet by a three-conductor cable and plug containing a protective ground conductor for [[Electrical safety standards|safety]]. When signal cables are connected between both devices, the [[shielded cable|shield]] of the signal cable is typically connected to the grounded chassis of both devices. This forms a closed loop through the ground conductors of the power cords, which are connected through the building wiring.

In the vicinity of electric power wiring there will always be stray [[magnetic field]]s, particularly from [[Overhead power line|utility lines]] oscillating at 50 or 60&nbsp;[[hertz]]. These ambient [[magnetic field]]s passing through the ground loop will induce a current in the loop by [[electromagnetic induction]]. The ground loop acts as a single-turn secondary winding of a [[transformer]], the primary being the summation of all current-carrying conductors nearby. The amount of current induced will depend on the magnitude and proximity of nearby currents. The presence of high-power equipment such as industrial motors or transformers can increase the interference. Since the conductors comprising the ground loop usually have very low resistance, often below one [[ohm]], even weak magnetic fields can induce significant currents.

Since the ground conductor of the signal cable linking the two devices is part of the signal path of the cable, the alternating ground current flowing through the cable can introduce electrical interference in the signal. The induced alternating current flowing through the resistance of the cable ground conductor will cause a small AC voltage drop across the cable ground. This is added to the signal applied to the input of the next stage. In [[audio equipment]], the 50 or 60&nbsp;Hz interference may be heard as a hum in the speakers. In a video system it may cause distortion or syncing problems. In computer cables it can cause slowdowns or failures of data transfer.

Ground loops can also exist within the internal circuits of electronic equipment, as design flaws.

Addition of signal interconnection cables to a system where equipment enclosures are already required to be bonded to ground can create ground loops. Proper design of such a system will satisfy both safety grounding requirements and signal integrity.  For this reason, in some large professional installations such as recording studios, it is sometimes the practice to provide two completely separate ground connections to equipment bays.  One is the normal safety ground that connects to exposed metalwork, the other is a technical ground for cable screens and the like.<ref>{{multiref|''BBC Engineering'', [https://archive.org/details/bbc-monographs-92/page/n34/mode/1up "Earth Fault Test Apparatus (EFTA)"], no. 82, p. 34, October 1972.|Julian Nathan, ''Back to Basics Audio'', p. 201, Newnes, 1998 {{ISBN|0750699671}}.|Philip Newell, ''Recording Studio Design'', p. 267, Taylor & Francis, 2013 {{ISBN|1136115501}}}}</ref>