Recent Changes to GR-1089-CORE

Released in May of 2011, GR-1089-CORE Issue 6 Electromagnetic Compatibility (EMC) and Electrical Safety requirements for Network Telecommunications Equipment has undergone a number of technical changes. We look at its substantial modifications and the potential impact on previously certified products.

Application Guidelines for Equipment Ports

Appendix B now defines two additional classifications for type 3 and 5 ports traditionally reserved for ports directly connected to metallic outside plant (OSP) lines. Intra-cell site cable ports directly connected to metallic OSP cables and located only at cell site or other locations that posses tall antennas are now classified as port type 3a/5a. The definition is further expanded by stating that this cable type has limited exposure as it is routed outdoors in relatively short distances, and that AC power fault conditions are not a significant threat. The greatest threat to type 3a/5a ports is due to Ground Potential Rise (GPR).

The second new classification is defined for short reach OSP cables. Cables that are deployed in short durations less than 500 feet due to functional design constraints are now classified as port type 3b/5b. Due to the short routing distances, type 3b/5b ports also have limited exposure to lighting and power fault conditions, and the greatest threat is posed mostly by near strike lightning.

Type 4 ports, which are traditionally reserved for customer premise or non-central office intra-building environments, now includes port type 4a for customer-side Optical Network Terminals (ONT’s) and Intelligent Network Interface Devices (iNID’s). These ports do not connect to metallic OSP lines and are intended to electrically or optically isolate ports from the network. Plain Old Telephone Service (POTS), Ethernet, and coaxial lines fall under port type 4a. However, coax lines are still tested as type 4 ports.

Type 8 ports, or DC power ports, includes two additional classifications. DC power routed to antennas or equipment located at the top of antennas is now classified as port type 8a. Type 8b covers DC power ports located in Intra-cell site environments. The test application chart for equipment ports located in GR-1089-CORE Appendix B has been updated to include these new port type classifications.

Electrostatic Discharge and Electrical Fast Transients

Section 2 continues to define the Electrostatic Discharge (ESD) and Electrical Fast Transient (EFT) requirements for network telecommunications equipment. A few minor technical changes were observed regarding ESD testing. The first was found under Requirement R2-2 which provides details regarding test methodology on performing contact discharge tests to non-conductive surfaces. R2-2 clarifies when performing contact discharge tests to non-conductive surfaces that produce arc discharges to surrounding conductive surfaces is not considered a valid test. Testing shall be repeated using air discharges at these locations, and results shall be deemed valid even where discharges are not observed. Additionally, Section 2.1.4.1 Test Methods Normal Operation states that if service effecting responses occur during testing, testing shall be repeated with longer intervals between discharges as referenced in the latest EN 61000-4-2 Version 2008 Test Standard.

Under the Electrical Fast Transients (EFT) Test Methods and Procedures Section, a statement has been added that permits the use of special software and firmware if it can be demonstrated that the EUT is configured and operated in a manner which is consistent with normal operation. This section has also been updated with special instructions regarding power ports, and using the capacitive coupling clamp versus the CDN method described in the latest version of IEC 61000-4-4. However, the CDN method is considered equivalent.

The EFT test levels, repetition rate, burst rate and burst period remains unchanged, which are consistent with IEC 300-386. However, GR-1089 still specifies the test levels for outside plant and central office intra-building ports (types 1 and 2) at 250 volts where EN 300-386 tests at 500 volts. The difference in screening levels for EFT prevents a product manufacturer from claiming CE mark compliance by test similarity, and will require conformance to the higher test level if they are intending to sell products in Europe. Another subtle difference noticed between the IEC test method and GR-1089 is the proposed test setup. Two illustrations have been included in issue 6 to address cable dressing during the test as shown in Figure 1. In these drawings, GR1089 depicts the coupling clamp positioned 1 meter from the EUT regardless of how long the cable under test is. This methodology is suggested by the standard of testing for each, but tends to deviate from the referenced IEC standard. IEC 61000-4-4 states that unless specified by the product manufacturer, the length of cable between the EUT and the coupling clamp shall be 0.5 m, ±.05 m. The IEC’s general laboratory test setup for EFT shown in Figure 2 suggests that for high entry or top fed ports, the coupling clamp shall be elevated such that no greater than one meter separation between the clamp the EUT exists. This requires installing an elevated groundplane and coupling clamp near the top of the cabinet. This may lead to incompatibility issues between GR and IEC if not addressed properly. For products that are being certified to EN 300-386 and GR-1089 I6 concurrently, it is recommended that the IEC method be observed as intended.

Radiated Emissions

In accordance with Section 3.1.4 FCC Part 68 and ACTA, technical criteria has been replaced with a statement regarding consolidated testing. GR1089 Issue 6 permits and encourages simultaneous testing to multiple standards such as FCC, EN 300-386, and GR1089. Consolidated test results are allowed in test reports. Traditionally, this has been common practice for global certification of telecommunications equipment and is expected to simplify the reporting requirements.

There has been a major change to the GR-1089 radiated emissions electric field requirements in Issue 6. R3-2[8] has been revised to state that radiated emissions electric field testing is performed from 30 MHz to 10 GHz intentional and unintentional radiators versus the previous 10 kHz to 10 GHz requirement in GR1089 Issue 5. However, the 3 and 10 meter limit levels have not changed for this new limited test range. The validity of the 10 kHz to 30 MHz test range has been in question for many years due to a number of reasons ranging from near field effects, correlation issues between an open area test site and shielded anechoic chambers and, more importantly, the actual need to measure radiated fields in this range. Emissions contributions in this frequency range are generally cable related and not emitted from the equipment enclosure. As GR-1089-CORE already quantifies conducted emissions from each cable type in this range, the elimination of this test frequency range is expected to be of limited risk.

Radiated Magnetic Emissions

Another major change observed in Issue 6 is that Section 3.2.1.3 Radiated Magnetic Field Emissions Requirement has been removed. The radiated magnetic emissions test was exclusive to GR-1089-CORE and was not an EN 300-386 OR FCC requirement. Therefore, this test requirement deletion has no impact on consolidated product certification. Traditionally, the radiated magnetic emissions limit was simply based on the conversion from electric field to magnetic field using the decibel equivalent of 377 ohms free space impedance of a plane wave, or -51.5 dB. These measurements were performed in two orthogonal axes and were useful in determining the magnetic component of the product emissions, but the results were of little use. Typically, if the product met the radiated electric field requirement they would meet the magnetic field requirement by default. Therefore, removal of this test requirement is considered to be of low risk to future product certification.

Conducted Emissions

Exclusive conducted emissions tests for analog voiceband leads previously, specified in GR-1089-CORE Issue 5 (Section 3.2.3.2 ), and conducted emissions for telecommunication leads (Section 3.2.3.3) have also been removed. However, they have been combined under the conducted emissions requirements for telecommunication ports in Issue 6. As similarly stated in Issue 5, all telecom ports require conducted current emissions measurements from 10 kHz to 30 MHz.

RF Immunity

In regard to RF immunity testing, Table 3-11 Frequencies of Key Interest has been updated. Television channel 2 (55.25 MHz), channel 11 (199.25 MHz), and channel 52 (699.25 MHz) have been excluded. However, additions to police/fire radio (481, 816, and 4965 MHz) have been added. Cell phone frequencies have been changed from 825 MHz to include 701, 711, 713, 781, 787.5, 791, 805.5, 1732, and 2310 MHz. PCS now includes 914 MHz in addition to 1800 MHz. In summary, GR1089 Issue 6 has specified 26 key frequencies versus 18 specified in Issue 5.

Lightning and AC Power Fault

Section 4 has undergone a variety of technical and formatting updates, including a new table (Table 4-2) which lists surge applicability based on port type. The table also provides a test surge description, test conditions, connections, and application information. The 23 newly listed surges appears daunting in size at first glance, but this is a consolidation of all first level lightning criteria into one table for quick and easy reference.

Intra-building Lightning

In regard to the first level intra-building lightning test criteria, GR-1089 now permits that either one surge can be applied to 3 samples or 5 five surges applied to one sample to ease the burden on vendors. However, using extended interval times between surges may be required when testing only one sample. R4-7 [233] states that all Ethernet ports shall be tested. However, type 2 Ethernet ports shall only be subjected to longitudinal (differential) surges. The use of either the 2/10 microsecond or the 1.2/50 microsecond waveform with stress levels between 800 and 1500 volts is still permitted.

GR-1089 has defined the double exponential impulse waveform and how to characterize its rising edge and duration times in Appendix A. This was traditionally performed between 10% and 90% of the rising edge, and between 0% of the rising edge and 50% of the falling edge for establishing the duration for both voltage and current waveforms as depicted in Figure 3. This holds true for most of the waveforms required in this new issue except for the 1.2 µs / 50 µs and the 10 µs / 700 µs combination waveforms, which only use this for current measurements. For the voltage component of these waveforms, they are characterized using 30% to 90% of the rising edge exclusively as shown in Figure 3. This methodology aligns with IEC 61000-4-5 as well as IEC 60060-1.

Figure 3: Double exponential voltage and current waveform measurements

Figure 4: Voltage measurements for the 1.2/50 µs, and 10/700µs double exponential waveforms

First Level Surges

There have been several changes to the first level surge test requirements as follows:
Surge 3 “Gas tube interaction test applicable for types 1, 3, 3b, 5b, and 5 ports” requires 4000V 10/700us V 5/310us A (ITU-T K.44 generator circuit schematic provided).

Surge 4 “Inductive kick test for OSP interfaces applicable for port types 1, 3, and 5.(???) 2500V 500 A 2/10us” is not required for ports solely intended for installation in GR487 or GR950 style enclosures. However, product labeling is required when the exclusion of Surge 4 is observed.

Surge 7 “High lightning exposure test for remote OSP interfaces” requires the 10/250 uS waveform be between 400V 50 A and 4kV 500 A.

Cell Site Inter-structure

Section 4.6.1.3 is a new test procedure which describes the withstand criteria for ports located within a cell site inter-structure. This section is intended for port interfaces which are deployed between separate structures, cabinets, buildings, and H frames within a cell site to mitigate potential GPR damage. Two separate test options are provided:

Option A: Isolation test – 1500 V AC 50/60 Hz 60 seconds
‑ 2120 VDC 60 seconds
‑ 10 2400V spikes 1.2/50 us

Option B: Surge Test
Types 3a, 5a or 8b ports
3a, 5 a ports are subjected to select intrabuilding surge tests (8 – 14.1)
3a, 52 and 8b ports are also subjected to 2.5 kV 5kA longitudinal surge (23 per Table 4‑2).

Second Level Lightning

In regard to the second level lightning surge criteria defined in Section 4.6.3, Table 4-3 now combines port type 1,3, and 5 with type 7 requirements into one table. However, there have been no technical requirement changes to these port types.

First Level AC Power Fault

Within the first level AC power fault criteria defined in Section 4.6.4, Table 4-4 has removed Tests 8 and 9 and tailored many of the test conditions. For the most part, the levels are slightly less severe than in GR1089 Issue 5.

Second Level AC Power Fault

A number of changes to the second level power fault test levels are shown in Table 4-5. The most substantial is that the maximum test voltage level has been limited to 425 V versus 600 V, but can be run at 600 V with manufacturer’s approval. Current remains at the same level as specified.

Enclosures Suitable for Fusing

GR-1089 Issue 6 has revised the requirements for equipment enclosures suitable for fusing. Requirement R4-55 [196] per GR0189 Issue 5 has been changed to R4-51 [196], which now states enclosures shall not contain vents or openings that would allow for ejection of molten metal, flames, or similar hazards when internal fusing occurs. No ventilation or opening were permitted in Issue 5.

R4-57 [198] per GR1089 Issue 5 requirement, which stated that the enclosure shall be capable of withstanding a 12-gauge shotgun blast without penetration of the enclosure wall by any pellets, has been removed.

Section 9 Bonding and Grounding

The most substantial change made in Section 9 of GR-1089 Issue 6 was that the embedded power sources defined rating has been reduced from >20 VA to >15 VA. This change has been reflected throughout the section, including short circuit testing which now states that a power source less than or equal to 15 VA need not be tested for short circuits. This has changed from 20 VA in issue 5. In addition, short circuit testing also states that all equipment that has been listed by an NRTL through standards such as UL60950 or UL1459 need not be tested for short circuits. This has changed from discrete equipment assemblies only as stated in Issue 5.

Section 10 DC Power Port Criteria

Section 10 has been updated to reference the new ATIS 0600315 test standard (formerly ANSI T1.315). The new ATIS document specifies that all transient voltage measurements are now specified to be made between 10% and 90% of the corresponding rising or falling edge of the waveform, which aligns with the IEC 61000-4-5 waveform characterization method.

In most cases, these transients are performed with a DC coupled audio amplifier while supplying the EUT with full load power. To verify this prior to testing, ATIS has provided 4 optional waveform verification methods which range from (1) open circuit, (2) with EUT in circuit, (3) resistive/capacitive load in circuit, or (4) purely resistive load in circuit. Although the fast rise and fall times are easiest to meet in an open circuit condition, additional tests are required to verify impulse current (100 amperes), as well as the amplifier’s slew rate in accordance with IEC-61000-4-11. However, any of the four optional verification methods are acceptable.

Another subtle change that was noticed was the ATIS 0600315 under voltage transient shown in Figure 5. The waveform’s fall time was relaxed to ≤ 12 microseconds from the 10 microseconds previously required by ANSI T1.315.

Among these changes, the noise returned by network equipment measurement specified by ATIS 0600315.2007 is no longer required per GR-1089 Issue 6. The wide band noise frequency test is still required by GR-1089, but with a relaxed limit requirement. This test measures the electrical noise (Vc) fed back from telecommunications equipment within any 3 kHz band ranging from 10 kHz to 20 MHz. For -48 VDC powered equipment, the limit (expressed in mV rms) 1.0 * square root of Ic (rated input current) or 1 ampere, whichever is greater, was changed to state that Ic or 10 amperes is now the maximum input current, whichever is greater. This change can substantially relax the wideband noise frequency emissions requirement for equipment operating at marginal loads.

There has also been a slight modification to the measurement circuit provided in ATIS 0600315 shown in Figure 6. The illustration provided in GR-1089-CORE Issue 6 (shown in Figure 7) introduces a high impedance transducer between the measurement equipment and the measurement capacitors to normalize the circuit impedance to at least 600 ohms. Notes provided in this revised section also state the capacitors are only used for voltage isolation and can be excluded if a differential probe is used.

In regard to the noise immunity test levels in Section 10, they have not changed for -48 VDC equipment except that voice frequency noise immunity is only reserved for products that include analog voice band ports.

Figure 6: ATIS 0600315 noise return circuit

Figure 7: GR‑1089‑CORE Issue 6 noise return circuit

Wireless Products Performance Requirements

Appendix F has been added in Issue 6 to address the minimum performance parameters for wireless products that must be monitored during immunity testing.

• Output RF PowerIn general terms, the forward power transmit levels shall remain within the manufacturers specified levels and tolerances, or ± 1 dB.
• FrequencyThe transmit frequency and bandwidths shall remain within FCC tolerable limits during and following testing.
• IntegrityThe transmitted modulated signal shall not lose any of its baseband information. Output power can be sampled and demodulated to monitor performance.
• Data error rateData error shall be within the manufacturer’s stated tolerance, not to exceed 1 %.

In summary, there have been a variety of technical changes which are intended to improve the electromagnetic and electrical safety certification process of network telecommunication equipment. However, these changes are still being evaluated by the RBOCs and have not yet been officially approved. For products intended to be sold to Verizon, Quest, and AT&T, GR1089 Issue 5 shall continue to be utilized until further notice.

References

ATIS 0600315 (2007) Voltage levels for DC Powered equipment used in the Telecommunications environment.

ANSI T1.315 (2001) Voltage levels for DC Powered equipment used in the Telecommunications environment.

GR-1089-CORE Issue 5 (August 2009) Electromagnetic Compatibility and Electrical Safety – Generic Criteria for Network Telecommunications Equipment.

GR-1089-CORE Issue 5 (May 2011) Electromagnetic Compatibility and Electrical Safety – Generic Criteria forNetwork Telecommunications Equipment.

ETSI EN 300 386 V1.4.1 (2008-04) Electromagnetic compatibility and Radio spectrum Matters (ERM); Telecommunication network equipment; ElectroMagnetic Compatibility (EMC) requirements.

61000-4-5 Second edition (2005-11) Testing and measurement techniques – Surge immunity test.

47 CFR Part 16 (2008) Federal Communications Commission regulations of intentional and unintentional electromagnetic emitters.

JEFFREY VIEL is the EMI/EMC engineering manager for National Technical Systems Boxborough, Massachusetts operations. He is an electrical engineer with over 15 years experience working in the EMI engineering industry. Jeffrey is considered a subject matter expert in multiple fields relating to electromagnetic interference design, and compatibility including lightning/power cross, shielding, bonding and grounding, and power quality filtering. He is also former sergeant in the U.S. Marine Corps, and long term member of IEEE, and SAE International, and an active member on several NTS/EMC related technical boards. Jeffrey currently provides technical training, product design consultation, EMI mitigation, test procedure development, and test/engineering staffing services to NTS clientele.