Direct answer: RRU power cable DC black 2×6 mm² is a two-core, 6 mm² flexible DC cable that carries −48 V from the BBU in the equipment room up the tower to the remote radio unit (RRU/AAU). "TFL" is not a generic cable type — it is Ericsson's own cable code family (TFL492324 = 2×6 mm²), and the "/0" suffix marks the black, UV-stabilised outdoor version; the plain code is the grey indoor version. The conductor is Class 5 tinned copper, rated 600 V, with XLPE or LSZH insulation, an aluminium-foil plus tinned-copper-braid shield, and an LSZH or PVC sheath.
Further reading: XLPO / XLPE / LSZH: What Are The Differences? · Cable Export Certifications Hub: EN 50618 / UL / CPR · H1Z2Z2-K / EN 50618 Solar Cable Guide · UK Cable Types to Chinese GB Equivalents · Cable Manufacturer Directory
1. Decoding the Name, Character by Character
| Element | Meaning | What buyers get wrong |
|---|---|---|
| RRU | Remote Radio Unit — the radio transceiver mounted at the tower top; RRH is the same thing under another vendor's name. 5G AAUs use the same DC feed | Confusing it with the RF jumper or the fibre run. The RRU power cable is DC power only |
| DC | Direct current, from the −48 V telecom power system (nominal −48 V, operating window roughly −40.5 V to −57 V) | Thinking "−48 V" means the cable is rated 48 V. It is not — see §3 |
| Black | Carbon-black pigmented, UV-stabilised sheath for outdoor tower installation | Assuming colour is cosmetic. Grey = indoor cabinet routing, black = outdoor UV |
| 2×6 mm² | Two cores, 6 mm² each — one +, one −. No earth core: the DC return is the second core | Quoting a 3-core or 1-core "equivalent" |
| TFL | Ericsson cable designation family. TFL492324 = 2×6 mm²; TFL492324/0 = the same cable with black UV-stabilised sheath for outdoor use | Treating "TFL" as a material or a standard. It is a part-number prefix |
The TFL nuance is worth money in a quotation. A buyer who asks for "TFL492324" wants the grey indoor version; "TFL492324/0" is the black outdoor one. Quote the wrong suffix and you ship indoor cable to a tower top, where the sheath chalks and cracks within a couple of seasons.
2. Construction — Five Layers, in Order
| # | Layer | Typical material | Notes |
|---|---|---|---|
| 1 | Conductor | Class 5 flexible stranded copper, tinned | Tinning stops oxidation and keeps crimp resistance stable at field termination; bare copper is available but not for humid/coastal sites |
| 2 | Insulation | Flame-retardant XLPE or LSZH polyolefin, black/grey or grey/blue | Per-core, 0.6–0.7 mm wall at this size |
| 3 | Inner shield | Aluminium/polyester laminate, ~100% coverage | Foil side out or in depending on design — the foil gives 100% coverage at high frequency |
| 4 | Outer shield | Tinned copper braid (or tinned copper-clad aluminium braid) | This is the low-frequency half of the shield; braid coverage 60–85% is typical |
| 5 | Sheath | LSZH (or PVC on cost-driven indoor items), black UV-stabilised or grey | Black sheath carries the carbon-black UV package; grey does not |
Two structural points that get lost in datasheets: the cable is insulation + shield + sheath — a three-layer build around the conductor, not a single jacket — and the two cores are laid parallel (flat-ish) in most RRU designs, which is why the dimensions appear as 9.5 × 9.5 mm rather than a single round diameter.
Why the shield is not optional on a tower. The RRU power cable runs in the same cable ladder as the RF jumpers and the fibre. A switching BBU power feed radiates; unshielded, it couples into the receive path and raises the noise floor. That is the whole reason the standard construction carries foil + braid, and it is why "shielded or unshielded?" is the first question in almost every RRU cable inquiry.
3. Electrical and Thermal Data (2×6 mm²)
| Parameter | Value |
|---|---|
| Rated voltage | 600 V (some makers rate 300/500 V — confirm on the datasheet, never assume) |
| System voltage | −48 V DC nominal, operating window ≈ −40.5 V to −57 V |
| Max DC resistance, 20 °C | ≤ 3.39 Ω/km per core |
| Max conductor temperature | 90 °C (XLPE or LSZH); 70 °C for PVC variants |
| Installation temperature | down to −40 °C |
| Approx. dimensions | 9.5 × 9.5 mm (shielded, 0.7 mm sheath) |
| Approx. weight | 141 kg/km |
| Min. bending radius | 12 × overall dimension (fixed); 6 × for flexible variants |
| Standard sizes | 2×2.5, 2×4, 2×6, 2×10, 2×16, 2×25 mm² |
The "rated 600 V on a 48 V system" question comes up in every second inquiry. The cable is rated 600 V because the rating covers switching surges, fault conditions and insulation-test practice — not because the system runs at 600 V. Do not let a buyer "downgrade" to a 48 V-rated part; there is no such telecom cable, and a thin-wall low-voltage part will fail the DC hipot and the flame test.
4. Sizing: the Voltage-Drop Trap on −48 V
This is where RRU cable projects actually go wrong, and it has nothing to do with the cable quality.
On a −48 V system the permitted drop is roughly 1.5–2 V per segment (the equipment needs ≈ −40.5 V at the RRU with a −53 to −57 V rectifier output). With 2×6 mm² at 3.39 Ω/km per core, the loop resistance is 6.78 Ω/km — double the single-core figure, because current goes up one core and back the other:
- 50 m run, 20 A → 0.339 Ω loop × 20 A ≈ 6.8 V drop — already over budget
- 50 m run, 10 A → ≈ 3.4 V drop — workable but tight
- Same 20 A on 2×16 mm² (1.24 Ω/km) → ≈ 2.5 V drop — comfortably inside budget
So: 2×6 mm² suits shorter drops and moderate RRU loads (classic 4G RRU), while 5G AAUs — which draw considerably more — usually push the specification to 2×10 or 2×16 mm². When a customer insists on 2×6 mm² for a 5G site, the right move is to show the voltage-drop arithmetic rather than simply accept the order; it is the fastest way to be trusted as a supplier instead of a parts counter.
5. Standards: What to Cite and What Not To
| Requirement | Standard normally cited |
|---|---|
| Conductor | IEC 60228 Class 5 (flexible stranded) |
| Design / insulation thickness | IEC 60502-1 (or the manufacturer's own spec) |
| Flame, single wire | IEC 60332-1-2 |
| Flame, bunched | IEC 60332-3-24 (Cat C) |
| Smoke density (LSZH) | IEC 61034-2 |
| Halogen content (LSZH) | IEC 60754-1 / IEC 60754-2 |
| US projects | UL 1581 (vertical flame / VW-1) — ask for the UL file number |
| China telecom | YD/T 2289 series (RRU cable); confirm the exact part and year against the project specification |
A caution on "UL 2731". It circulates in RRU cable marketing copy, but the standard that actually appears on RRU power cable datasheets and test reports is UL 1581 (or UL 44 / UL 83 for the wire construction). If a buyer asks for UL, give them a file number and the standard it was tested to — printing "UL 2731" without a report behind it is the kind of claim that fails at goods-inspection.
6. Selection and Quotation Checklist
- Shielded or unshielded — the single most frequent clarification in RRU inquiries. Tower-top and outdoor: shielded. Short indoor BBU-to-cabinet runs: unshielded is acceptable.
- Sheath compound — LSZH is mandatory for many European and CPR-driven projects; PVC is cheaper and common on domestic indoor runs. Never substitute silently.
- Black or grey — outdoor vs indoor, and on Ericsson codes this is the
/0suffix. Get it in writing on the PO. - Conductor: tinned or bare — tinned for humid, coastal and offshore sites; bare only when the buyer explicitly accepts it.
- Cross-section against load and run length — do the §4 arithmetic before confirming 2×6 mm² for a 5G site.
- Certification set — collect flame, smoke, halogen and (if claimed) UL documents per batch, not per year.
- Brand names on the datasheet — describe the cable as "for RRU/AAU DC power in FTTA installations", and reference OEM part codes (e.g. TFL492324/0) only as a cross-reference in the quotation. Do not print "compatible with Huawei / ZTE / Ericsson / Nokia" as if it were an approval — it is not, and buyers' compliance teams know it.
7. Ready-to-Send Reply (for inquiries)
This is RRU DC power cable 2×6 mm², black UV-stabilised sheath for outdoor tower installation, supplying −48 V DC to the remote radio unit. Conductor is Class 5 flexible tinned copper, insulation XLPE or LSZH, with aluminium-foil plus tinned-copper-braid shield, rated 600 V, 90 °C conductor, max DC resistance 3.39 Ω/km per core. For Ericsson projects the equivalent code is TFL492324/0 (the "/0" is the black outdoor version; TFL492324 without "/0" is grey indoor). Please confirm two points before we quote: shielded or unshielded, and LSZH or PVC sheath — and tell us the run length and RRU load so we can check the voltage drop on −48 V.
FAQ
Q: What does "TFL cable" mean — is it a standard? A: No. TFL is Ericsson's cable designation family (TFL492322 / 492324 / 492325 / 492326 ...). The number identifies size and construction; the "/0" suffix means black UV-stabilised sheath for outdoor use, while the code without "/0" is grey indoor cable. It is a part-number system, not a material or a standard.
Q: Is a 600 V rated cable necessary for a −48 V system? A: Yes. The 600 V rating covers switching surges, fault conditions and insulation testing practice on telecom DC plant. There is no "48 V rated" RRU cable on the market, and thin-wall low-voltage substitutes fail hipot and flame testing.
Q: Why is the RRU power cable shielded if it only carries DC? A: Because it is routed in the same ladder as RF jumpers and fibre. A switching DC feed couples noise into the receive path; the aluminium foil plus tinned copper braid keeps the power cable from degrading the radio's noise floor.
Q: Can 2×6 mm² be used for a 5G AAU? A: Often not. 2×6 mm² has a loop resistance of about 6.78 Ω/km, so a 50 m run at 20 A already drops roughly 6.8 V — beyond the −48 V budget. 5G sites typically move to 2×10 or 2×16 mm². Always check run length and load before confirming the size.
Q: What is the difference between the black and grey RRU power cable? A: Sheath compound. Black contains carbon-black and a UV stabiliser for outdoor tower exposure; grey is for indoor cabinet and equipment-room routing and has no UV package. Same conductor, same insulation — different service life outdoors.
