Recommended use D, yn11 tie line transformer recent years, the use of the system in TN D Nanyang high voltage power distribution room design the most reasonable, yn11 tie line group of the transformer is very common, but there are many projects still use Y, ynO knot line group of transformers, the main reason is not clear advantage of the former. In GB50052-95 "supply and distribution system design" in Article 6.0.7 states: "In the low-voltage grid TN and TT earthing system type, and should use D, yn11 tie line group as a three-phase transformer distribution transformers . " Here, "should use" grounds, mainly based on D, yn11 tie line than Y, ynO tie line transformer has the following advantages: 1) in favor of the higher harmonic current suppression. And more than three times higher harmonic excitation current in the primary access into △ shape conditions, can form a loop Nanyang distribution room running record in the primary, help suppress harmonic current distribution room, to ensure the quality of the supply waveform. 2) in favor of the unit ground fault fault removal. Because D, yn11 tie line than Y, zero sequence impedance of the line is much smaller knot ynO Nanyang distribution room setup requirements, the transformer single phase power distribution system to expand more than three times the short-circuit current, it is beneficial to the single-phase ground short circuit fault resection. 3) the ability to take full advantage of the device of the transformer. Y, ynO tie line neutral current transformers require no more than 25% of the rated current of the low voltage winding (see Section 6.0.8 GB50052-95 article), severely limiting the contact with the single-phase load capacity, affect the ability of the transformer device fully utilized; and D, the neutral current transformer yn11 junction line phase current is allowed to reach more than 75%, even up to 100% of the phase current, so that the capacity of the transformer can be fully utilized, which is a large single-phase load capacity system is very necessary. Therefore, low-voltage grid type TN and TT earthing system, the recommended D, yn11 tie line group of distribution transformers. 1) High beam: Some design considerations when ceiling height without taking into account the height of the beam. Due to the large span substation, sometimes up to about the height of the beam 800mm, so the mention of civil conditions should be considered storey height of the beam. 2) the duty room: Some designs will set up in inaccessible duty room in the corner. This article does not comply with the provisions of Section 4.1.6 of GB50053-94, which states "manned substation, duty room should be set separately. High voltage power distribution room and duty room should be straight or communicated through the channel, duty should direct access to the outdoors or walkway leading to the door, "3) cable channel: Some double substation layout set only low voltage distribution panel and the rear end of the trench at the screen, do not communicate with each other between the two rows of the screen ditch . In order to facilitate future access and adjust the cable line, should all the main cable channel and control all communication with the internal cable channel. Nanyang distribution room overhaul faster _ Teflon electricity (certified) _ distribution room provided by Nanyang Fulong Power Engineering Company Limited. Nanyang Fulong Power Engineering Co., Ltd. (www.nyfulong.com) is Nanyang, Henan, transmission equipment and materials leaders, over the years, the company is implementing the scientific management, innovation and development, the principle of honesty and trustworthiness, and satisfy customer needs. Teflon leader in power with the staff warmly welcome all inquiries negotiations to create Teflon power a better future.