Safety - Revision history

Pstch at 12:05, 22 August 2019

2019-08-22T12:05:51Z

Pstch at 12:00, 22 August 2019

2019-08-22T12:00:38Z

Pstch at 11:57, 22 August 2019

2019-08-22T11:57:01Z

Pstch at 11:56, 22 August 2019

2019-08-22T11:56:44Z

Pstch: Formatting

2019-08-22T11:56:31Z

Formatting

Pstch at 11:56, 22 August 2019

2019-08-22T11:56:06Z

Pstch at 11:55, 22 August 2019

2019-08-22T11:55:15Z

Pstch: Add warning

2019-08-22T11:55:05Z

Add warning

Pstch at 11:51, 22 August 2019

2019-08-22T11:51:05Z

Pstch: Create safety page

2019-08-22T11:50:25Z

Create safety page

New page

As with all electrical systems, great care must be taken to keep the system safe and avoid injuries and equipment damage. Different systems are used for different hazards, and the characteristics of the electrical system (voltage, max current, user exposition) determines the required protections.

== Isolation, earthing and residual currents ==

Electrical circuits must be isolated from their environment, and conductors must be isolated from other conductors. Earthing (grounding) is used to keep the exposed condutive parts close to earth potential, so that we can avoid electrical shock and electrocutions. Earthing is also useful to protect against lightning strikes, and it can improve the behaviour of residual current detectors.

Even in the case of very low-voltage circuits, there are multiple reasons why proper earthing can be required :
* Voltage doesn't kill, but current does. In some conditions, even 12V will be able to pass through a body and stop a heart or even fry everything.
* Voltage is not always guaranteed : over-voltage systems have their limits, and you may be on the wrong side of this system, in which case the over-voltage situations can get even worse as the circuit is opened.
* It can help for the operation of some over-voltage protections (surge suppressors)

== Over-current protection ==

An over-current condition is defined as a conductor/equipment carrying more current than it has been designed for. This situation is handled by opening the circuit, usually after a delay (to allow start-up peaks), using a thermal breaker (that opens the circuit after it has heated up to a certain level).

== Fault/short-circuit protection ==

A current fault condition is defined as a conductor/equipment carrying "abnormal" current, where the current is "abnormal" in either/both its value or its rate of change. This situation can occur in the case of a "short-circuit", but also when the circuit is accidentally connected to a different circuit (for example, accidentally connecting a DC grid to the mains). This situation is handled by opening the circuit very quickly (because the fault current can be very high), using a magnetic breaker (that opens the circuit based on the rate of change of the current).

== Over-voltage protection (also under-voltage) ==

An over-voltage condition is defined as two conductors having a difference in potential that is out of the specified range. This situation can occur in the case of non-managed excess supply, or rapid unloading. It must be avoided because it can damage equipments, changes the operational characteristics of other safety devices, and decreases the resistance required to avoid carrying a current (increases the risk of an electrical shock).

Under-voltage should ideally also be handled, as it can damage equipments and confuse an user/operator into thinking that a circuit is not connected to power. Under-voltage can occur in the case of lack of supply, or rapid loading.

TODO: Describe how to handle these situations, add links to the existing circuit designs

@@ Line 1: / Line 1: @@
-'''NOTE:''' This document was not written by an electrical engineer, its author doesn't have enough knowledge and experience to be confident enough in its content.
+* '''NOTE:''' This document was not written by an electrical engineer, its author doesn't have enough knowledge and experience to be confident enough in its content.  ''' ANYTHING DESIGNED USING THIS CONTENT SHOULD BE REVIEWED BEFORE ACTUAL USAGE'''. Please don't shock yourself.
-''' ANYTHING DESIGNED USING THIS CONTENT SHOULD BE REVIEWED BEFORE ACTUAL USAGE'''.
+* '''TODO: Find someone to review and validate this content.'''
 As with all electrical systems, great care must be taken to keep the system safe and avoid injuries and equipment damage. Different systems are used for different hazards, and the characteristics of the electrical system (voltage, max current, user exposition) determines the required protections.
@@ Line 18: / Line 15: @@
 There are multiple earthing schemes that can be used for DC circuits.
-'''TODO: Describe earthing schemes and their relation to micro-grids and their structure'''
+* '''TODO: Describe earthing schemes and their relation to micro-grids and their structure'''
 == Over-current protection ==
 An over-current condition is defined as a conductor/equipment carrying more current than it has been designed for. This situation is handled by opening the circuit, usually after a delay (to allow start-up peaks), using a thermal breaker (that opens the circuit after it has heated up to a certain level).
 == Fault/short-circuit protection ==
 A current fault condition is defined as a conductor/equipment carrying "abnormal" current, where the current is "abnormal" in either/both its value or its rate of change. This situation can occur in the case of a "short-circuit", but also when the circuit is accidentally connected to a different circuit (for example, accidentally connecting a DC grid to the mains). This situation is handled by opening the circuit very quickly  (because the fault current can be very high), using a magnetic breaker (that opens the circuit based on the rate of change of the current).
 == Over/under-voltage protection ==

@@ Line 1: / Line 1: @@
-'''NOTE:''' This document was not written by an electrical engineer, its author doesn't have enough knowledge and experience to be confident enough in its content. '''
+'''NOTE:''' This document was not written by an electrical engineer, its author doesn't have enough knowledge and experience to be confident enough in its content.
-ANYTHING DESIGNED USING THIS CONTENT SHOULD BE REVIEWED BEFORE ACTUAL USAGE'''.
+''' ANYTHING DESIGNED USING THIS CONTENT SHOULD BE REVIEWED BEFORE ACTUAL USAGE'''.
 Please don't shock yourself.

← Older revision		Revision as of 11:56, 22 August 2019
Line 1:		Line 1:
−	'''NOTE:''' This document was not written by an electrical engineer, its author doesn't have enough knowledge and experience to be confident enough in its content. ''' ANYTHING DESIGNED USING THIS CONTENT SHOULD BE REVIEWED BEFORE ACTUAL USAGE'''. Please don't shock yourself.	+	'''NOTE:''' This document was not written by an electrical engineer, its author doesn't have enough knowledge and experience to be confident enough in its content. '''
		+	ANYTHING DESIGNED USING THIS CONTENT SHOULD BE REVIEWED BEFORE ACTUAL USAGE'''.
		+	Please don't shock yourself.

	'''TODO: Find someone to review and validate this content.'''		'''TODO: Find someone to review and validate this content.'''

← Older revision		Revision as of 11:56, 22 August 2019
Line 1:		Line 1:
−	~~<big>~~'''NOTE:''' This document was not written by an electrical engineer, its author doesn't have enough knowledge and experience to be confident enough in its content. '''	+	'''NOTE:''' This document was not written by an electrical engineer, its author doesn't have enough knowledge and experience to be confident enough in its content. ''' ANYTHING DESIGNED USING THIS CONTENT SHOULD BE REVIEWED BEFORE ACTUAL USAGE'''. Please don't shock yourself.
−
−	ANYTHING DESIGNED USING THIS CONTENT SHOULD BE REVIEWED BEFORE ACTUAL USAGE'''. Please don't shock yourself.~~</big>~~

	'''TODO: Find someone to review and validate this content.'''		'''TODO: Find someone to review and validate this content.'''

← Older revision		Revision as of 11:56, 22 August 2019
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	ANYTHING DESIGNED USING THIS CONTENT SHOULD BE REVIEWED BEFORE ACTUAL USAGE'''. Please don't shock yourself.</big>		ANYTHING DESIGNED USING THIS CONTENT SHOULD BE REVIEWED BEFORE ACTUAL USAGE'''. Please don't shock yourself.</big>
		+
		+	'''TODO: Find someone to review and validate this content.'''

	As with all electrical systems, great care must be taken to keep the system safe and avoid injuries and equipment damage. Different systems are used for different hazards, and the characteristics of the electrical system (voltage, max current, user exposition) determines the required protections.		As with all electrical systems, great care must be taken to keep the system safe and avoid injuries and equipment damage. Different systems are used for different hazards, and the characteristics of the electrical system (voltage, max current, user exposition) determines the required protections.

@@ Line 15: / Line 15: @@
 * Voltage is not always guaranteed : over-voltage systems have their limits, and you may be on the wrong side of this system, in which case the over-voltage situations can get even worse as the circuit is opened.
 * It can help for the operation of some over-voltage protections (surge suppressors)
 == Over-current protection ==
@@ Line 31: / Line 35: @@
-TODO: Describe how to handle these situations, add links to the existing circuit designs
+'''TODO: Describe how to handle these situations, add links to the existing circuit designs

← Older revision		Revision as of 11:55, 22 August 2019
Line 1:		Line 1:
−	<big>'''NOTE:''' This document was not written by an electrical engineer, its author doesn't have enough knowledge and experience to be confident enough in its content. '''ANYTHING DESIGNED USING THIS CONTENT SHOULD BE REVIEWED BEFORE ACTUAL USAGE'''. Please don't shock yourself.</big>	+	<big>'''NOTE:''' This document was not written by an electrical engineer, its author doesn't have enough knowledge and experience to be confident enough in its content. '''
		+
		+	ANYTHING DESIGNED USING THIS CONTENT SHOULD BE REVIEWED BEFORE ACTUAL USAGE'''. Please don't shock yourself.</big>

	As with all electrical systems, great care must be taken to keep the system safe and avoid injuries and equipment damage. Different systems are used for different hazards, and the characteristics of the electrical system (voltage, max current, user exposition) determines the required protections.		As with all electrical systems, great care must be taken to keep the system safe and avoid injuries and equipment damage. Different systems are used for different hazards, and the characteristics of the electrical system (voltage, max current, user exposition) determines the required protections.

@@ Line 18: / Line 18: @@
 A current fault condition is defined as a conductor/equipment carrying "abnormal" current, where the current is "abnormal" in either/both its value or its rate of change. This situation can occur in the case of a "short-circuit", but also when the circuit is accidentally connected to a different circuit (for example, accidentally connecting a DC grid to the mains). This situation is handled by opening the circuit very quickly  (because the fault current can be very high), using a magnetic breaker (that opens the circuit based on the rate of change of the current).
-== Over-voltage protection (also under-voltage) ==
+== Over/under-voltage protection ==
 An over-voltage condition is defined as two conductors having a difference in potential that is out of the specified range. This situation can occur in the case of non-managed excess supply, or rapid unloading. It must be avoided because it can damage equipments, changes the operational characteristics of other safety devices, and decreases the resistance required to avoid carrying a current (increases the risk of an electrical shock).