IEEE 3004.11-2019 pdf free download – Recommended Practice for Bus and Switchgear Protection in Industrial and Commercial Power Systems.
Apreventive maintenance pragram is essential to detect deterioration, to make repairs, and to check and best relays, trip units, control systems, and creuitbreaker performamcee before a futoccurs (see IEEE SId 3007.21M [B16]). The detrte propetties of isuating materials can deteriorate over time particulaty ifthe equipmnent is subjcct to gete-tan-standard temperatures or transicnt overvoltage conditions.
Moving mechanical parts can become ificult to move because of a loss of lubricity in lubriants and bonds formed at joints, and electronic capacitors can lase capacitance ower time. Proper maintenance is a integral part of equipoment protection, safety, and optimization of capital investments.. Proper implementation of safty practioes such as those described in NFPA 70E, require that mainenance of electrical equipment be properly conducted fllowing manufacturers’ instructions or gencrally acepted industry practices. Modem protesctive relays, trip units, and control ystems can measure, monitor, and calculate panmeters important to implement conditin-based maintenance. Modem electromic devices with appropriate communiations capabilities can monitor each other as well as implement sytem-wide protection functions to fcilitatee sten-wide maintenance and protecton. In aditioto proper mintetaee, consideration should be given to including instrumentation and sensing devices of functions useful to diagnose power-systerm and cquipment problens that might occur over the life of the equipnent.
Powerful muhifunction digital meters. modem controls and protection devics llows rermote control of equipment for greater safety and fexibiliy. Remote diagpostie capability llows experts located in remote locations to toubleshooe problems a the equipment rgrdles of pbysical lcation. Regardless of the steps taken tw avoid bus futs, such fauts occasionally occur. High-speed protective relaying, direee acting potetion (integral trip unit), or apopriatcly rated fisss should be used to minimize fult duration.n Raupid clearing tims limit damag, minimie arc -Aush eneny, and mitigte the efe of short circuits om otber parts of tbe power system. Providing proper bus pouetiton requires a wll-designed system. Fach equipmeant assembly should be provided with a main protective device for cach power source, either as an integral part of the asembly. or in a remole location, protecting the incoming line. In some cases, it might be advisble to install the main devie in a dedicated and separate sction to manually isolatc the line-side bus fom the source if adequate protection of the line-side bus Cannot be obtained to suficienly reduce arc-fash incident-energy values. If the min protestive device is omitted im an smbly and provided by a remote line side orourent device, the intillatianon my be acepiable if the device provides appropriate protection; bomever, the lack of a local disonneet may not be opimal for mainenance purposes.
The main circuit breaker sometimes is omited a the scondary of a power transformer when the scondary feeder breakers have ratings that adequaely proteet the transformer from overloading, This topology might reduce the efctvenese of secondary bus protection beceuse the transfomer reduces the sensitivity of the primary protection for secondary fults unless specife protection schemes are put in place to properly deal with the situation, like transformer dfferential that inchudes the secondary side bus within its zone of protectiom.
When power systems are grounded through a risance or reactance to limnit fault damage, the shr-circuit current awailable to detect a ground fault is smaller and requires more sensitive protective relaying. A deha-wye transtfomer comnection rfleets a secondary ground fult curent through two primary plhase windings.
The reduced value of current at the primary makes secondary ground fault currents in solidly grounded secondary transformers mare dificult to detect. When the sccandary of the transformer is impedance grounded, a secondary side ground fult may be indistinguishable from load for relays o the primary side and, hence, providing scondary side semsitive ground-ault relaying is important to itiate the opening of all soures that can feed the fault (800 IEEE SItd 2421-2001 (IEEE Bu) Bookim, Chapier 8 (B12])’ When supplementary brstifertrtal protective relaying, zne-seletive iterlocking (ZSD), or any other method is used to isolate bus fuls, it is essential that the method openate omly for bus and switchgear faults. False tipping on extemal faults is, generally, unaccptable.IEEE 3004.11 pdf download