Protection Relay – ANSI Standards h ttp ://e l e c tri c a l - e n g i n e e ri n g - p o rta l .c o m/p r o te c ti o n - re l a y - a n s i - s ta n d a rd s
J a n u a r y 23, 2013
In t he design design of elect electri rical cal power syst syst ems, t he ANSI Standard Device Numbers denot Numbers denote e what what f eatures eat ures a prot ectiv ect ive e device device support support s (such (such as a relay or circuit breaker). These types of devices protect elec protect electt rical rical systems systems and component compo nents s f rom damage damage when an unwanted unwant ed event event occurs, such as an electrical electrical faul f aultt . ANSI ANSI numbers are used t o ident ify if y the th e funct f unct ions of medium medium voltage volt age microprocessor microprocessor devices. devices. ANSI ANSI f acilitat acilitat es the t he development o f American National Standards (ANS) by accrediting the procedures of standards st andards developing developing organizat ions (SDOs). (SDOs). T hese groups wo rk cooperatively to develop voluntary national consensus st andards. andards.
Protection Relay - ANSI Standards
Accreditat Accredita t ion by ANSI ANSI signif signif ies t hat t he procedures used by t he standards st andards body in connect co nnect ion with t he development development of o f Americ American an Nat National ional Standards meet meet t he Inst Institut itut eâs eâs essential requirements for openness, balance, consensus and due process.
ANSI standards (protection) â index Curr Current ent protec tion f unctions unctions ANSII 50/51 â Phase overcurrent ANS ANSII 50N/ ANS 50N/51N 51N o r 50G/51G 50G/51G â Ear Eartt h fault or sensit sensit iv ive e eart eart h faul f aultt ANSII 50BF â Br ANS Breaker eaker f ail ailure ure ANSII 46 -Negative ANS -Negat ive sequence / unbalance ANSII 49RM ANS 49RMS S â Thermal overload
Dir ect ect ional ional power power prote prote ction f unctio unctions ns ANSII 32P â Di ANS Directional rectional act iv ive e o verpower ANSII 32Q/40 â Di ANS Directional rectional reactive o verpower
Voltage Voltage prot protect ect ion functions ANSII 27D â Positive sequence undervolt ANS undervolt age ANSII 27R â Rem ANS Remanent anent underv undervolt olt age ANSII 27 â Phase-to-phase undervoltage ANS
ANSI 59 â Phase-t o-phase overvoltage ANSI 59N â Neutral voltage displacement ANSI 47 â Negative sequence voltage
Recloser ANSI 79 â Reclose t he circuit breaker aft er t ripping
Directional current prote ction ANSI 67 â Directional phase overcurrent ANSI 67N/67NC â Directional earth f ault ANSI 67N/67NC t ype 1 ANSI 67N/67NC t ype 2 ANSI 67N/67NC t ype 3
Machine protect ion f unctions ANSI 37 â Phase undercurrent ANSI 48/51LR/14 â Locked rot or / excessive starting t ime ANSI 66 â Starts per hour ANSI 50V/51V â Voltage-restrained o vercurrent ANSI 26/63 â Thermost at, Buchholz, gas, pressure, t emperature det ection ANSI 38/49T â Temperat ure monit oring by RTD
Frequency protection f unctions ANSI 81H â Overfrequency ANSI 81L â Underfrequency ANSI 81R â Rate of change of f requency (ROCOF)
Current protection functions ANSI 50/51 â Phase overcurrent
Three-phase protection against overloads and phase-to-phase short-circuits. ANSI 50N/51N or 50G /51G â Earth fault
Earth f ault prot ection based on measured or calculated residual current values:
ANSI 50N/51N: residual current calculated o r measured by 3 phase current senso rs ANSI 50G/51G: residual current measured directly by a specific sensor ANSI 50BF â Breaker failure
If a breaker fails to be t riggered by a tripping order, as detect ed by the non- extinct ion of t he f ault current, this backup prot ection sends a tripping order to t he upstream or adjacent breakers. ANSI 46 â Ne gative se quence / unbalance
Prot ection against phase unbalance, detected by the measurement of negative sequence current: Sensitive prot ection t o detect 2-phase fault s at t he ends of long lines Prot ection of equipment against t emperature build-up, caused by an unbalanced power supply, phase inversion or loss of phase, and against phase current unbalance ANSI 49RMS â Thermal overlo ad
Prot ection against t hermal damage caused by overloads o n machines (transformers, mot ors or generat ors). The t hermal capacity used is calculat ed according to a mathematical model which t akes into account: Current RMS values Ambient t emperature Negative sequence current, a cause of mot or rot or t emperature rise ANSI index â
Recloser ANSI 79
Aut omation device used t o limit do wn t ime aft er tripping due to t ransient or semipermanent f ault s on overhead lines. The recloser orders automat ic reclosing of the breaking device af t er t he t ime delay required to resto re the insulation has elapsed. Recloser o peration is easy t o adapt for diff erent operating modes by parameter sett ing. ANSI index â
Directional current protection ANSI 67 â Direct ional phase o ve rcurrent
Phase-t o- phase short -circuit prot ection, with selective tripping according to f ault current direction. It comprises a phase overcurrent f unction associated wit h direction det ection, and picks up if t he phase overcurrent f unction in the cho sen direction (line or busbar) is activated f or at least one of t he 3 phases. ANSI 67N/67NC â Direct ional earth fault
Earth f ault prot ection, wit h selective tripping according t o f ault current direction. 3 types of operation: t ype 1: t he prot ection f unct ion uses the projection of t he I0 vect or t ype 2: t he prot ection function uses t he I0 vecto r magnit ude wit h half -plane t ripping zone t ype 3: t he prot ection function uses t he I0 vecto r magnit ude wit h angular sector t ripping zone ANSI 67N/67NC t ype 1
Directional eart h fault prot ection for impedant, isolat ed or compensated neut ralsystems, based on t he project ion of measured residual current. ANSI 67N/67NC t ype 2
Directional overcurrent prot ection f or impedance and solidly eart hed systems, based on measured or calculat ed residual current. It comprises an earth f ault f unction associated with direction detection, and picks up if t he eart h fault f unction in the chosen direction (line or busbar) is activated. ANSI 67N/67NC t ype 3
Directional overcurrent prot ection for distribut ion networks in which the neutral earthing system varies according to the operating mode, based on measured residual current. It comprises an earth fault function associated with direction detection (angular sector tripping zone defined by 2 adjustable angles), and picks up if t he earth f ault f unction in the cho sen direction (line or busbar) is activated. ANSI index â
Directional power protection functions ANSI 32P â Directional active overpower
Two-way protection based on calculated active power, for the following applications: active overpower protection to detect overloads and allow load shedding reverse active power prot ection: against generat ors running like mot ors when t he generat ors consume active power against mot ors running like generators when t he mot ors supply active power ANSI 32Q/40 â Directional reactive overpower
Two -way prot ection based on calculated reactive power to detect f ield loss on synchronous machines: react ive overpower prot ection for mot ors which consume more reactive power wit h field loss reverse reactive overpower prot ection for generato rs which consume reactive power wit h field loss.
ANSI index â
Machine protection f unctions ANSI 37 â Phase unde rcurrent
Prot ection of pumps against t he consequences of a loss of priming by t he det ection of mot or no-load operation. It is sensitive to a minimum of current in phase 1, remains stable during breaker tripping and may be inhibit ed by a logic input . ANSI 48/51LR/14 â Locked rot or / excessive start ing time
Prot ection o f mot ors against overheating caused by: excessive mot or st arting t ime due t o overloads (e.g. conveyor) or insuff icient supply voltage. The reacceleration of a mot or t hat is not shut do wn, indicated by a logic input , may be considered as starting. locked rot or due t o mot or load (e.g. crusher): in normal operation, af t er a normal start directly upon starting, before the detection of excessive starting time, with detect ion of locked rot or by a zero speed det ecto r connected t o a logic input, or by t he underspeed f unction. ANSI 66 â Starts pe r hour
Protection against motor overheating caused by: t oo f requent starts: motor energizing is inhibited when t he maximum allowable number of starts is reached, af t er count ing of : starts per hour (or adjustable period) consecutive mot or hot or cold starts (reacceleration o f a motor t hat is not shut down, indicated by a logic input, may be count ed as a start) starts t oo close t oget her in t ime: mot or re-energizing aft er a shut down is only allowed aft er an adjust able waiting time. ANSI 50V/51V â Voltage-restrained overcurrent
Phase-to-phase short-circuit protection, for generators. The current tripping set point is voltage-adjusted in order to be sensitive t o f ault s close t o t he generator which cause voltage drops and lowers t he short-circuit current. ANSI 26/63 â Thermostat/Buchholz
Prot ection of t ransf ormers against t emperat ure rise and int ernal f ault s via logic inputs linked to devices integrated in the t ransfo rmer. ANSI 38/49T â Te mperature monitoring
Protection that detects abnormal tem erature build-u b measurin the tem erature inside
equipment f itt ed with sensors: t ransf ormer: prot ection of primary and secondary windings motor and generator: protection of stator windings and bearings. ANSI index â
Voltage protection functions ANSI 27D â Positive seque nce undervoltage
Prot ection of mot ors against f ault y operat ion due to insuff icient o r unbalanced network voltage, and detection o f reverse rot ation direction. ANSI 27R â Re manent unde rvoltage
Prot ection used t o check that remanent voltage sustained by rot at ing machines has been cleared befo re allowing the busbar supplying the machines t o be re-energized, t o avoid electrical and mechanical t ransients. ANSI 27 â Undervoltage
Prot ection of mot ors against volt age sags or detect ion o f abnormally low net work voltage to t rigger aut omat ic load shedding or source transf er. Works with phase-to- phase volt age. ANSI 59 â Overvoltage
Detection of abnormally high network voltage or checking for sufficient voltage to enable source transfer. Works wit h phase-t o- phase or phase-t o- neutral volt age, each volt age being monito red separately. ANSI 59N â Neutral voltage displacement
Det ection of insulat ion f ault s by measuring residual volt age in isolated neutral systems. ANSI 47 â Negative se quence overvoltage
Prot ection against phase unbalance result ing f rom phase inversion, unbalanced supply o r distant f ault , detected by t he measurement of negat ive sequence volt age. ANSI index â
Frequency protection functions ANSI 81H â Overfrequency
Detect ion of abnormally high f requency compared t o t he rated f requency, t o monit or power supply qualit y. ANSI 81L â Underfrequency
Detect ion o f abnormally low f requency compared t o t he rat ed frequency, t o monitor power
supply quality. The prot ection may be used f or o verall t ripping or load shedding. Prot ection stabilit y is ensured in the event of t he loss of t he main source and presence of remanent voltage by a restraint in t he event of a cont inuous decrease of t he frequency, which is activated by paramet er sett ing. ANSI 81R â Rate o f change of fre quency
Prot ection f unction used fo r fast disconnection o f a generato r or load shedding cont rol. Based on t he calculat ion of the frequency variation, it is insensit ive to t ransient voltage disturbances and theref ore more stable than a phase-shif t protection f unct ion. Disconnection In installations with autonomous production means connected to a utility, the ârate of change of f requencyâ prot ection f unct ion is used to detect loss of t he main system in view of opening the incoming circuit breaker to: prot ect t he generat ors f rom a reconnection witho ut checking synchronization avoid supplying loads outside t he installation. Load shedding The ârate of change of f requencyâ prot ection f unct ion is used for load shedding in combination with the underfrequency protection to: eit her accelerate shedding in t he event of a large overload or inhibit shedding f ollowing a sudden drop in f requency due to a problem t hat should not be solved by shedding. ANSI index â
