Grounding

Product Details :

LATAR BELAKANG
Salah satu metoda pentanahan Trafo Tenaga adalah dengan  menggunakan NGR. NGR adalah sebuah tahanan yang  dipasang serial dengan neutral sekunder pada transformator  sebelum terhubung ke ground/tanah. Tujuan dipasangnya  NGR adalah untuk mengontrol besarnya arus gangguan  yang mengalir dari sisi neutral ke tanah. Hal ini terkait  dengan Pola pengamanan Trafo Tenaga disisi Sekunder  (Sistem Distribusi).
Neutral Grounding Resistance (NGR) adalah komponen  yang dipasang antara titik netral trafo dengan pentanahan,  dan Neutral Grounding Resistance (NGR) berfungsi untuk  memperkecil arus gangguan yang terjadi.
Ada dua jenis NGR, Liquid dan Solid

Liquid
berarti resistornya menggunakan larutan air murni yang
ditampung didalam bejana dan ditambahkan garam (NaCl)
untuk mendapatkan nilai resistansi yang diinginkan

Solid
Sedangkan NGR jenis padat terbuat dari Stainless Steel,
FeCrAl, Cast Iron, Copper Nickel atau Nichrome yang  diatur sesuai nilai tahanannya.

KEGUNAAN
1. Neutral Grounding Resistor digunakan untuk resistance grounding pada sistem tenaga industri. Umumnya  dihubungkan antara ground dan netral dari trafo, generator  dan grounding transformer.

2. Neutral grounding resistor digunakan untuk membatasi arus  gangguan maksimum sampai ke nilai yang tidak merusak  peralatan pada sistem tenaga, tetapi cukup untuk  mengoprasikan relay untuk menghilangkan gangguan.

FUNGSI
Mengurangi arus gangguan satu fasa yang muncul di jaringan  listrik tegangan mengengah untuk mencegah kerusakan pada  transformer dan generator.

Product Details :

NGT (Neutral Grounding Transformers)

Resistance grounding systems protect power transformers
and generators from damaging fault currents. Low
resistance grounding of the neutral limits the ground fault
current to a high level (typically 50 amps or more) in order
to operate protective fault clearing relays and current
transformers. These devices are then able to quickly clear
the fault, usually within a few seconds. The limited fault
current and fast response time also prevent over-heating
and mechanical stress on conductors.
If the system has a neutral which is available, a single
phase distribution transformer can be used in conjunction
with a loading resistor to provide high resistance
grounding. This is particularly well suited for grounding of
generators, in that it allows the system to operate like an
ungrounded system under normal conditions, while still
retaining the ability to limit ground fault current. The
primary of the transformer is connected from the system
neutral to ground. The loading resistor is connected
across the transformer secondary. The resistor is normally
sized to allow a primary ground fault current in the range
of 2 to 12 amps and is typically rated for either one minute
or continuous duty. The transformer should be sized
accordingly, with a primary rating equal to the system line
to neutral voltage and the secondary normally rated 240 or 120 volts.
When a ground fault occurs downstream of the grounding transformer, ground fault current flows through
the fault and back through ground to the grounding transformer. The loading resistor limits the current
flow in the secondary winding, which in turn limits the flow of the ground fault current back into the system
through the primary of the grounding transformer.
Post Glover’s GT product line is designed for applications on systems up to 15kV. Secondary voltage is
typically 240 volts, and resistors are designed according to customer specification. Typical construction is
a dry type transformer with a secondary resistor mounted in a common enclosure..