ABB HU Manuals

Instruction Leaflet All possible contingencies which may arise during installation, operation or maintenance, and all details and variations of this equipment do not purport to be covered by these instructions. If further information is desired by purchaser regarding this particular installation, operation or maintenance of this equipment, the local ABB Power T&D Company Inc. representative should be contacted. Printed in U.S.A. CAUTION ! Before putting relays into service, remove all blocking which may have been inserted for the purpose of securing the parts during shipment, make sure that all moving parts operate freely, inspect the contacts to see that they are clean and close properly, and operate the relay to check the settings and electrical connections. I APPLICATION These relays have been specially designed and tested to establish their suitability for Class 1E appli- cations. These relays have been specially designed and tested to establish their suitability for Class 1E applications in accordance with the ABB Power T&D Company program for Class 1E Qualification Testing as detailed in bulletin STR-1. “Class 1E” is the safety classification of the electric equipment and systems in nuclear power generating stations that are essential to emergency shutdown of the reactor, containment isolation, cooling of the reactor, and heat removal from the containment and reactor, or otherwise are essential in preventing sig- nificant release of radioactive material to the environ- ment. The types HU and HU-1 relays are high-speed relays used in the differential protection of transformers. These relays can be applied where the magnetizing inrush current to the transformers is severe. Current transformer ratio error should not exceed 10% with maximum symmetrical external fault current flowing and the maximum symmetrical error current which is flowing in the differential circuit on external faults should not exceed 10 times relay tap setting. The HU-1 relay has three restraint transformers and associated rows of taps; whereas, the HU relay has one less restraint transformer and two rows of taps. Otherwise the two relays are identical. Three-winding banks normally require the HU-1 relay, although the auto-transformer application uses the HU if the ter- tiary is not loaded. Both the HU or the HU-1 are available with a sensitiv- ity of either 30% or 35% times tap. The 30%-sensitiv- ity relay satisfactorily handles up to 15% mismatch (e.g. ± 10% transformer tap changing plus 5% ct mis- match). The 35%-sensitivity relay handles as much as 20% mismatch. See figure 7 for a comparison of the characteristics of the two sensitivities. Any of the relays may be recalibrated in the field to obtain either characteristic. Ordinarily the 30%-sensitivity relay will suffice; how- ever, where ct mismatch is abnormally high or where the transformer tap-changing range exceeds 10%, this calibration may be too sensitive. I CONSTRUCTION The types HU and HU-1 relays consist of a differen- tial unit (DU), a harmonic-restraint unit (HRU), an indicating instantaneous trip unit (IIT) and an indicat- ing contactor switch (ICS). The principal parts of the relay and their locations are shown in figures 1, 2, 3, and 4. 41-347.12C Effective: February 1999 Supersedes I.L. 41-347.12B, Dated November 1998 ( | ) Denotes Change Since Previous Issue Type HU and HU-1 Transformer Differential Relays (Class 1E Applications) ABB Automation, Inc. Substation Automation & Protection Division Coral Springs, FL Allentown, PA

Instruction Leaflet 41-347.1S Ami MINI ABB Power T&D Company Inc. Relay Division Coral Springs, FL 33065 Type HU, HU-1 and HU-4 Transformer Differential Relays Effective: April 1991 Supersedes 41-347.1R, Dated April 1987 (|) Denotes Change Since Last Issue File No. E103204 the restraint transformers of the HU and HU-1 relays are connectedin parallel, andtheIIT pickup of these relays is ten times the relay tap value. On the other hand, the rectified outputs of the restraint transform- ers of the HU-4 relay are connected in series, and theIIT-unit for this relay is set at fifteentimes the tap value. Otherwise, the three relays are identical. Three-winding banks normally require the HU-1 re- lay, although the auto transformer application uses the HU if the tertiary is not loaded. The HU-4 is par- ticularly applicable to protect a transformer and bus section combination. It also may be applied to three- windingtransformers with one side connectedto two breakers. CAUTION Before putting relays into service, remove all blocking which may have been inserted for the purpose of securing the parts during shipment, make sure that all moving parts operate freely, inspect the contacts to see that they are clean and close properly, and operate the relay to check the settings and electrical connections. These instructions apply to the following types of relays: • HU • HU-1 The HU, HU-1 and HU-4 are available with a sensi- tivity of either 30% or 35% times tap. The 30% sen- sitivity relay satisfactorily handles up to 15% mis- match (e.g., ±10% transformer tap changing plus 5% ct mismatch). The 35% sensitivity relay handles as much as 20% mismatch. See Figures 13 and 14 for a comparison of the characteristics of the two sensitivities. Any of the relays may be recalibratedin the field to obtain either characteristic. • HU-4 1. APPLICATION The types HU, HU-1, and HU-4 relays are high speed relays used in the differential protection of transformers. These relays canbe applied where the magnetizing inrush current to the transformer is severe. Current transformer ratio error should not exceed 10% with maximum symmetrical external fault cur- rent flowing andthe maximum symmetrical error cur- rent which is flowing in the differential circuit on ex- ternal faults should not exceed 10 times relay tap setting. The types HU, HU-1, and HU-4 relays have two, three, or four restraint transformers, respectively, and associated rows of taps. The rectified outputs of Ordinarily the 30% sensitivity relay will suffice; how- ever, where ct mismatch is abnormally highor where the transformer tap-changing range exceeds ±10%, this calibration may be too sensitive. Z CONSTRUCTION The types HU, HU-1 andHU-4relays consist of a dif- ferential unit (DU), a harmonic restraint unit (HRU), an indicating instantaneous trip unit (NT) and an All possible contingencies which may arise during installation, operation, or maintenance, and all details and variations of this equipment do not purport to be covered by these instructions. If further information is desired by purchaser regarding this particular installation, operation or maintenance of this equipment, the local Asea Brown Boveri representative should be contacted. Printed in USA Courtesy of NationalSwitchgear.com